i think it's a wrong impression, try it. it's not super social; for this you can try instagram. but some flickr groups are just amazing. i am learning so much, training my eye...

YMMV but I've been a happy Flickr customer for over a decade. They haven't modernized much so the site looks and feels old, but their pricing is very fair and there are still a lot of folks on it.

I have considered selfhosting myself, but it's a lot of work and features like "auto upload from my phone" and "privacy guard for pictures of my kids, but make login-free links for grandparents" are very nontrivial.

I agree, Flickr has lost its spark. It might be dying, it might not. But whatever it had is gone.