I tried doing that with Twitter a few years ago in an attempt to reduce the amount of posts related to US politics. I don't follow any political figures or commentators, only tech people and artists, but about half the posts on my feed were about US politics.

Although I ended up with a blocklist of around 100 words it was very much a losing battle and a waste of time.

But if people are forced to pick a hashtag, then they will want to correlate around one hashtag. So many things could be releated to politics.