Just anecdotally, I noticed that more junior team members were FAR more willing to ask me for help with something after we were pulled back to the office. That can be mitigated with thoughtful collaboration efforts when operating fully remote, but I didn't even know they needed help until they could just pop by my desk and ask for something. And they started doing it frequently.

But to be clear, I greatly prefer full remote for myself and again, thoughtful approaches to team management can solve or mitigate a bunch of the remote work downsides, probably.

with WFH it's generally harder to analyze what areas the worker is struggling, and it also lacks the one on one with the worker. You can still technically do a video call or screen-share but, it's harder to monitor the worker to verify that said mentorship is taking effect, without compromising the privacy of the worker and the system at hand. It's possible to do but, you lose many tools such as constant monitoring of multiple under-performers at once that make it harder to actually monitor and mentor. This is without including that remote work is much harder to actually monitor work activity vs work productivity until it is too late(end of day, missed deadline, etc).