I have never seen this feature on any social media platform.

Good, then we can have it as an exclusive Steemit feature if we're not able to have subgroups (like Subreddits).

What you can do is only follow the people that you enjoy their content. Then occasionally throughout the day, switch over to Trending or Hot. Problem solved in the interim.

Frankly, if I have to do that, I won't ever remember to do it and people will stay unfollowed. Also, the stuff I don't care to repetitively see still shows up, which I don't want at all, so this is not really a resolution at all, in fact it's barely a band-aid. This isn't a matter of follow/unfollow. I want to straight up MUTE those topics so I don't have to keep moving past them like obstacles.

There are instances here where I have users I would love to follow because I DO enjoy some of their content, and I even interact with them on their posts. But then those same users may have content I would just rather avoid all together. I don't want to unfollow or mute that person, just those topics.
This should absolutely be an option.