I agree that this seems to be an issue for new hires that I've seen.

But I think the blame for this lies in management and the seniors on the team. If a fresh out of college grad feels hesitant to ping a coworker then that coworker is doing something wrong. I'm seeing a lot of companies and teams seem to shift this blame to the WFH situation, where really it is a failure of the team to not integrate and work well together in a shifting situation.

Plenty of companies that are remote first have no issue mentoring junior engineers, so I don't see what the excuse is for companies that are not.