A couple of the apps do have this “multi community” feature, if you’re a mobile user. Summit definitely does, Raccoon (the one I’m replying from now) technically does but it’s pretty broken so I’m hoping that gets looked at soon. And tbh maybe more of them do now, it’s been a while since I checked!
Unfortunately that link doesn’t help much. Currently among the list of “recommended instances” (followed by a claim that it “doesn’t matter” which of these you choose) are a French-speaking instance, a crypto instance, and an anime instance. Hardly welcoming places for your average person, unless you happen to be a French crypto bro looking for porn in which case you are definitely well catered for.
OP might not have all the details worked out but their point is a good one, and it’s an issue on Mastodon as well. It’s all well and good having a one-liner description about each instance but it can be quite a trawl to find the actual important info you need to make a decision.