Yeah, that’s a you thing. I have accounts on six or seven instances so far. No disappearing communities at all, posts usually loading fine unless there’s an issue with a specific instance. Comments can be sparse, but that’s a matter of patience. Posts that invite discussion get comments, it just takes longer. The flip side of that is that you can comment everywhere and be certain your comment didn’t get buried, and that there’s a higher chance of it leading to discussion because of that
I can’t say why you’re experiencing the issues, it could be the app. Could be your instance being one that’s kinda not well liked and being defederated by more than the average. Could be your instance just fucking up in general (I’ve seen statements that lemmy.ml is a little unstable currently). And it could be that you just haven’t run across the things that interest you, which may or may not be helped by anything since not every interest has a big community at all, even on a bigger service like reddit.
But the stuff you’re specifically pointing to aren’t happening for everyone, no.