Despite the many errors and evils wrought by modern-ism in theology, I suspect that modern-ity† has in many ways, and perhaps on balance, been good for the discipline of theology. If I were trying to make this case, it would include at least some of the following reasons:

1. There are more theologians writing and reflecting from the different Christian perspectives than ever before. This is of course a mixed blessing at scale — but close to an unalloyed good for any given aspiring theologian. Some of the gatekeeping imposed on the discipline by the combination of medieval technology and institutions was good, and some was bad, or at least counter-productive, for the discipline’s health. Broadly speaking, before the technological and institutional revolutions of modernity, only the bishops (or those in their favor) could produce works of theology, which unavoidably limited the scope of theological writing (ruling out many heresies) and put any aspiring theological writer more or less at the mercy of his or her bishop’s opinions (on whether a certain heresy might or might not be latent in their work). Without in any way wishing to disavow the Church’s proper role as convener and authorizer of theologians, a certain freedom from scrutiny is of course necessary for really creative thought to come to full flower, and it seems to me hard to dispute that the Church’s bishops have not always scrutinized correctly or had sufficient patience with budding theological minds. (To take the most extreme example: one can only imagine how the early years of Reformation might have proceeded differently had the already hot-headed Luther been met by less intransigent bishops and papal emissaries.) There is no past golden era of free-flowing thought in theological education, not even when an Albertus Magnus taught in the University of Paris; that golden era in a way really is now, for some of the reasons that follow.
2. Along with this goes the possibility of a better, richer mutual understanding of those different Christian perspectives. It really is remarkable, when reading pre-modern theological writers, not just the degree of vitriol they often exhibit against their opponents (especially in Reformation-era polemics) but how frequently they misrepresent or indeed misunderstand them as well. This, like most of my other observations, applies less often to the genuinely top echelon of theologians — Sts. Augustine, Thomas, Gregory, et al. — as to those closer to the middle of the bell curve; compare Richard Hooker’s generally temperate and perceptive (even, occasionally, sympathetic) approach to the arguments of his presbyterian opponents, to his forerunner John Jewel’s rather more vehement approach to the arguments of his Romanist opponents! But those in the middle of the bell curve are still often influential in their own days, even if they are later remembered only as foils to the greater thinkers who moved beyond and reacted against them; think of the way that Gabriel Biel is now utterly forgotten as a theologian in his own right and his thought is only taught as the background (for good or ill) to Martin Luther’s theology. It is better if those generationally, if not millennially, influential theologians have a more rigorous and a more charitable understanding of their opponents' positions. One of the great accomplishments of the ecumenical movement has been the reversal of sweeping anathemata against those Christians outside one’s own tradition, and the recognition that, say, Roman Catholics and Lutherans genuinely have much to learn from one another about justification (aside from not being as far apart in the first place as the rhetoric suggested).
3. This has partly resulted in, and partly been begotten by, the modern revolution in hermeneutics: hermeneutics considered not in its pre-modern sense as the set of rules for reading and interpretation, but in its contemporary philosophical sense as deep reflection on the act of reading, the problem of historical understanding, and the construction of meaning. To be sure, “revolution” really might overrate the degree of discontinuity; much of what is apparently new in Schleiermacher and Gadamer can also be found, in at least inchoate form, in, say, St. Augustine. Nevertheless, we have now in the contemporary world these significant hermeneutical possibilities: a chastened understanding of the “literal sense” that admits the unfixedness and unparaphraseability of textual meaning while simultaneously accepting its reality and its real effects; an appropriately moderated view of what can and cannot be established about a text on the basis of allegorical readings (as well as the fluidity of what constitutes “allegorical reading”); a proper admission of the inescapability of personal prejudices in interpretation and the indissoluble role of trust in knowledge; a fuller, if never full, perception of how a text’s “history of effects” (Wirkungsgeschichte) influences how it is read by me today; a recognition of the dialectic structure of thought and the complexity of acceptance. It has taken several centuries, but modernity has provided us with this methodological foundation — a methodological foundation which, ironically, should free us from too great a concern for closely observing properly “historical” methodology.
4. To the hermeneutical — if not “revolution” at least “evolution” — may be added what should fairly be called the text-critical revolution. We have more widespread and straightforward access to more theological works, from more perspectives and periods of Christian history, in ever more accurate texts, than at any previous point in Christian history. This has opened up genuinely new frontiers for theological interactions that would have faced exceedingly greater obstacles, or simply did not exist, hundreds of years ago. (One wonders, for example, how Calvin’s theology might have differed had he read St. Thomas without mediation, or for that matter St. John of Damascus at all.) You really can bring Karl Barth and Pseudo-Dionysius into conversation, and you might find that you want to — and when you do, you have the benefit of the most accurate texts of the Areopagite, freed through long scholarly labor from the corruptions that unavoidably creep in as texts are manually copied and recopied over centuries. Not to mention that we have an enormous text-critical apparatus for that Book which is the fountainhead and norma normans of all theology, that is, the Bible; though much of the value of that apparatus is found in recognizing (cf. Brevard Childs) the theological judgments that accompanied the Bible’s transmission, beyond questions about its most accurate or probably original text (we should, of course, have an appropriately chastened view of such historical judgment calls).
5. My last reason — for now! — may seem a curious one. In displacing Christendom, the secularity of modern civilization re-awakens the urgency of many crucial theological questions which could be taken for granted in an era of greater assumed cultural consensus. Today there is a critical need for a thick theological anthropology and doctrine of creation (almost the same thing) precisely because what it means to be a human creature is so contested in the secular world. Similarly there is a great need for a theological reckoning with the fact and reality of cultural and theological plurality. Or — take issues where the Church’s historical record is more lamentable. One of the only good effects from the unmitigated disaster that was the Shoah has been the long-overdue Christian reckoning with the degree to which reflexive anti-Judaism and its racialized descendant anti-Semitism had infiltrated our civilization and thinking; hardly any Christian preacher would today be willing to deploy the invective which a St. John Chrysostom or a Martin Luther hurled at the Jews. Similarly, the crisis of “gender roles” brought on by first industrialization and then feminism has, for all its enormous fallout, helped to illumine how remarkably sloppy has been much historic Christian reflection on what it means to be, and what is possible/permissible for, a woman — that is, when it has been reflected upon at all, rather than simply taking up unbaptized and unconverted notions from pagan culture or philosophy. For the Church to consider more deeply than before what is really true about God, the world, and herself is always an unalloyed good, even when this consideration is (as it usually is) for reasons of controversy and tragedy. Secularity is in countless ways a great (and occasionally self-inflicted) tragedy, but the Church’s business is discovering the redemptive effects of tragedy — just as it is her God’s business.

For all these reasons, and no doubt more I have not articulated here, I am grateful to live in modernity, despite wishing I could do away with the bad fruit of modernism in myself and in others. The correct answer to “When in history would you like to live?” should always be “Right now.” This is in part a simple matter of the honor that is due to Providence. But it is also a matter of recognizing the particular gifts of Providence in and for this time: as long as it is called “today.”

† At least, modernity in its “first watershed,” to crib Ivan Illich’s opening gambit in Tools for Conviviality.