What about good old IRC
There are several mobile IRC apps around, not to mention embedded chats on websites that work just as well if you don't want to download an app.
"The thing is, Discord is a place where most people are. "
^ This is sort of the lynchpin of the entire Web2.0 exodus. The herd mentality is strong. But, to break out of it someone has to be first. You can't start a community by just expecting it to already be there when you arrive. I think the best strategy would be to start small, find a couple friends who also don't like Discord and get a small chat going. Then share your (hopefully positive) experience with others. People need to be shown an alternative, just saying "Discord bad" won't change much at all. Also telling people about an alternative is not as good as actually using and promoting that alternative (note to self lol)
I agree about being the change that you want to see, but it's so hard to find new resources that have even a small community. I am here because I am longing for that life on the Internet before most of us went to the same three websites/apps. Anyway, do you have any IRC apps that you recommend? Or, any websites with IRC chats you use?