When I had instagram, I used to private message every new follower that came in.
It was copy-paste for the most part, but it wasn’t automated. I hand delivered over 24,000 messages over a 4 year time span and if someone responded I always made a best effort to kickoff a conversation or follow up with a question related to them.

Not sure if it helped anyone, when I went all in on Nostr I blew up those accounts. Part of me just wonders if I could build something similar yet wildly more valuable to others at the same time!