we all kind of collectively decided that.
part of what made discord take over is that it's easy. you push a few buttons and you're in, and you have a wide array of quality-of-life shit. you can drop images or videos in, you get link previews, you get synced experiences on whatever clients you have. it's all pretty trivial and zero-effort -- everyone has one now. it's also trivial to get started with your own server (and then have its channel count balloon out of control). they have really smoothed out pretty much all of the rough edges.
any alternative is going to have to go up against that, and discord has a lot of money behind it. good luck.
there are a few other options people have suggested.
there's "matrix", which is enough of a mess that i've heard several people give it an honest shot and then give up when inevitably it's a nightmare to configure/maintain -- basically, XMPP 2.
there's "guilded", which, uh, if you weren't aware -- some people keep seriously suggesting it -- is owned by roblox, the "scam kids out of work for play money" company. yeah, no thanks. i'll pass on that one.
someone suggested slack, which was kind of funny. you know what people want out of a friend chat platform? a single account for each server, and every server is limited to only showing you a very limited amount of history unless you pay wildly. slack is not a casual platform.
then there's, uh, irc? which nobody uses because it lacks all of the above features that make people use discord. oh boy, if i want to have multiple connections at once, now i have to set up a bouncer, and god forbid i want push notifications, sharing, or voice.
there are no good alternatives. it's like how chrome took over the internet -- provide a better user experience, make it streamlined, get everyone on it, and then you win. watch everyone else die.
even if you find a better option, or are willing to put up with a sub-par experience... other people have to do that, too. it's why people are still on twitter even when the site is lurching into the night sky next to an iceberg -- a ton of people are still there. even fi you're wiling to tolerate the simplicity of irc, or the configuration nightmare of matrix, or god-knows-what, you have to get that buy-in from every single person you want to work with, or... nobody is going to move, because why would they. as much as this other platform sucks, all your friends are there and it "works".

