While it's probably based on engagement, it's still a flaw of the algorithms I feel. Just because other people engages more with the content, doesn't mean it's the correct content for a given hashtag / following.

For instance, I mostly follow cycling and running stuff on IG. The suggestions / explore feed is therefore full of women in short running shorts and bicycle jerseys with the zipper down. It's not really that relevant content considering what I actually follow, but I think the engagement those things get push all other cycling / running related content away.