A sentiment I've heard multiple times over the last couple of days, and one that I feel is not at all fair.
Updating any form of software tends to break its dependencies. Just look at Unity: it's littered with deprecated methods. Even if there is official mod support, there is no guarantee that any update won't break those 'supported' mods (as plenty of games with mod support will show you). The only way the modding community would no longer be 'screwed' if is Re-Logic stopped releasing updates whatsoever. If we're really going to think in absolutes here, then it's a choice between screwing the modding community, or screwing the entire community.
But even then, that statement holds no ground. Terraria has no official mod support, no. Because if you develop a game, you pretty much have to build it with mod support in mind: trying to incorporate it afterwards is an order of magnitude more complicated and time consuming (time that could be spent on developing actual content). When Terraria was written, the developers had no idea that it would become as successful or as large as it has (which admittedly, is extremely impressive), so mod support wasn't a primary concern (note that this was all before the Steam Workshop came out). And thus it still hasn't got any, because of how time consuming it would be.
So despite not having official mod support written in the software, Re-Logic actively supports community modding, going as far as allowing actual modifications to the main executable (the developers that allow that are few and far between, and doing it without permission is in fact illegal). Not only that, but Re-Logic has a history of hiring their programmers from the modding community, and their current programmers are active in the tModLoader discord helping out whenever and wherever they can.
If that is 'screwing the modding community', then quite genuinely I don't know what else to tell you.