How are you going about joining different communities and managing your engagement? Are you only participating on the community on your instance? Are you joining and posting in as many instances that seem relevant?
For now I subscribe to multiple communities, but I really hope the Lemmy devs figure out a way to let each user create a community group.
The way I envision it is that you can create a group where you can combine communities on your end, and you can then cross-post to these communities when you post to that community group.
On the other hand, there would need to be a way to ensure that cross-posts aren't generating a ton of duplicates to those subscribed to multiple communities, and I'm not sure how the comments on these cross-posts should be dealt with. Maybe the comments should be kept separate per cross-post, or maybe if you have these communities in a group there could be a way to display the comments from there multiple posts together, to ensure all those crossposts have a change to get some interaction on other instances?
Then there's also the possibility of spammers abusing the system.
I like the idea of viewing multiple communities. However, I don't like the idea of cross-posting to all communities at the same time - it would prevent communities with overlapping topics to diverge and specialise, since people would mostly post the same stuff in all of them.
Instead I think that a multireddits-like approach is better: you group comms for visualisation, and your group can be either private or public. If public, other people can copy your group, so they use it instead of subscribing to individual comms.