It kills any ongoing conversation, and imo, convinces newcomers that people don't so much chat in that Discord as they just press shiny buttons.
But when the majority of conversations are happening in forums/thread style channels then it works well. You can still have some more niche chat style sections where typically 2-10 people participate
Chat channels are also fine for lots of people when its not about conversations but more just about sharing things. Like a "Share what you build" or "memes" channel work well as tons of messages are fine as you only care to see a few anyway.
Also limited size voice channels can be good aswell 5 people max.
I used to just engage with my friends. Now it feels like a really noisy reddit. Sure I could leave all of them, but that is kind of my point. There is an identity crises for the product.