By asking that question I think you've identified part of the problem, because around the time Covid started we lost a very competent senior dev and nobody has been hired to replace him.

Still, I used to have some pretty cool impromptu conversations in the hallway with people from other teams about projects they're working on at home, and they were great to learn from. With WFH I'd have never met some of those people. No idea how to recreate that environment.