I hate the discordification of communities. A lot of them did not survive the modern era and moved en masse there, but the experience is miserable, and they're usually moderated in a manner that doesn't spur discussion ("move to this section for X topic", et cetera, that's just one I see often). Finding content? You have to use some weird bot or the awful search function worthy of a high school assignment website project. Besides, it's also difficult to access it from my recent experience. You can provide a valid email and phone number, validate, and it may still suspend you for "violating ToS" (?) immediately after signing up. I don't think it's suited for a lot of things that end up on there, that shouldn't really be in IM-form, but maybe it's just old-me.
That's actually my number one issue with Discord: the stratification of discussion. With IRC, your "community" is a singular channel where everyone congregates and talks. It can be chaotic, and maybe you only check in and catch up so often, but it's all in one place.
Discord groups always end up with 735 channels about super specific topics. So you're not only spreading discussion over tons of channels where things will be evenly quiet and unnoticed, but you now have to go and laboriously check each of them to find new stuff. Or mute half of them you don't care about so you're not constantly being spammed with unread indicators. This also creates the "internet cop" problem, where whoever created the community (or someone they added as a moderator) feels the need to constantly yell at people for having organic discussions instead of searching for the specific channel approved for topic #365.
Basically, the whole thing seems to discourage discussion more than foster it, because people simply don't work that way. That sort of structure works for forums, but not for something happening in real time.
The "human" aspect of discord annoyed me too much, there's indeed a lot of seriousness brought by the "possibilities" of the app and the spirit of today where everything has to be classified. People are becoming very tense about information, it's like music shows with smartphone filming except with admins in a chan.
