I always think FB/Meta is about to go the way of Myspace with a popularity drop off but I'm clearly biased as I deleted my account years ago and people still talk about using FB a lot.
I think the ad spam was what did it. There was enough already, but it’s way over the top now. I had to constantly stop and check if I was seeing something relevant, as though there was never a long enough break from it to just enjoy my friend’s photos.
I imagine that's actually the point. IG has little need to build for the people currently on Instagram. They're getting that ad revenue already. Their goal is to get new people to join IG and trigger ad views, and TikTok proved that there's a huge crowd of people that can provide for that goal. They just need to expand the product to appeal to them. So that's what they did.
Once Instagram Stories started more and more real friends started just posting Stories clips and less photos and updates. Now my feed has all my friends just posting random Stories clips, and actual photos are dominated by advertising and influencers.
Facebook of old was like what the OP was saying. IG is only marginally like that with friends pic posts.
This is regardless of whatever tiktok stuff since I don’t use IG much for the same reasons as OP.
Maybe it's just my country but I can find anyone I know or work with on there by typing their name in.
Obviously though that is being eroded away by Instagrams lack of confidence and insistence to fight TikTok, which I also find strange I mean yeah its a vertical feed of video but really why you go to it is really different for why you go to IG, TikTok has more in common with YouTube than IG.