Opt-in versus opt-out. Active versus passive. A lot of mentorship is just role modeling, juniors observing how seniors conduct themselves in various situations by proximity.

$DAYJOB might as well be fully-remote since the team is heavily distributed and it's the same problem.

I think it's a problem for all workers, not just juniors. Maybe 1 person in the org sees the whole elephant. Way too many "organizational branch mispredictions" from incomplete mental models colliding.