You over-analyze everything. Instagram is better than facebook because of its simplicity and better design - mostly due to hashtags. Small accounts can reach viral thanks to their content and good use of the hashtags already with numbers existing in the UI. Why change that then, no point.
People don't go to IG because "highers up are already there" xD, they go to IG because it's simple. They know they gonna see only nice photos, videos not some stupid posts with ideological bullshit. They see what they like, they click like, follow, comment, SIMPLE.
So why instagram will die without numbers? Because literally every teenager, model, influencer, photographer, chef, dog, cat, meme, traveler, architect etc. cares about numbers and is addicted to them. Also sponsors, investors like those numbers visible, delete numbers - delete money.