Discord is such a terrible platform for large scale communication.
Nothing pisses me off more than looking for a support link and being told you have to go to a discord. It’s terrible to search, generally requires a bunch of hoops to jump through verifying you’re not a bot and almost never has the info you’re looking for anyways.
Plus Discord is a shitty company removing features from paid users (custom tags) and forcing changes to be more like Twitter.
Along with only having 100 slots available for non-Nitro users. Even with Nitro it's 200.
Between social spaces and games I play (some with several servers just for different classes), I don't have much space left for random topics. I'm clearly a heavy Discord user, but it is not the place for forums for all the reasons you listed too.