The problem about the current state of hashtags in the fediverse is that users have a fragmented view on posts, depending on their instance. Some posts containing a hashtag never reach your own instance, so you won't see it. This is bad for decentralisation and coordination.
I plan to throw some additional P2P stuff at the fediverse: All instances are distributing the responsibility for relaying or storing posts (just their IDs) among themselves using a Distributed Hash Table. ->