I think the problem of instagram is most people use bots nowadays which is annoying. There is not much real engagement on the platform, most is fake.

Here on steem you also have bots but i think it may be a better system. Because when content is to spammy people will start to flag and then it's costing money for the spammer.

Instagram bots are free to use (not all but a lot of them are) and easy to use that's why there is much spam. You could easily make multiple accounts and spam the sh*t out of them. When an account get's banned you simply make another one. Here on steemit you could also do that but it will cost you money when people start flagging. So there is less of an incentive to do so.