Not all the different services talk to each other in a way that you can use just 1 account for the entire fediverse. Lemmy, Piefed and Mastodon can all cross communicate (tho afaik Mastodon is one way only-you can post to Lemmy from Mastodon, but not Lemmy to Mastodon); but none of them communicate with Matrix. So you need at least 2 accounts if you wanted to use all of these services.

Different services have different functions, even within microblogging and different apps support different sites, don't think any support all services on activityhub at once.

That's absolutely NOT the whole point.
The main point is to avoid vendor lock-in, and monopolistic abuses.

If you make a pixelfed account somewhere and want to follow Lemmy conversations, you'll have trouble for a number of reasons.

i only stay on one platform at a time, i only move if something significant happens to lemmy. i wouldnt be able to keep up with that many, it does sound like its more than op can handle.