Firstly, there is the unstoppable flood of new posts that are added while browsing "All". Although this doesn't happen when using the Jerbea app, it sometimes renders "All" unusable in the browser.

This will be resolved once websockets are removed with the next update:

https://github.com/LemmyNet/lemmy/issues/3008

Secondly, the issue of the same posts being displayed for days under "Hot". There is already a pull request for this, so it has been fixed and just needs to be implemented:

https://github.com/LemmyNet/lemmy/issues/3076

These two other improvements are also essential in my opinion, but I don't know if there are any plans by the devs to realize them:

1. Links to external instances should automatically be transformed when opened so that one can participate with the account of their own instance. For example, lemmy.world/c/memes should automatically become feddit.de/c/memes@lemmy.world.

2. Communities from different instances should be able to merge, allowing users to see the content of all communities across different instances.