A junior learns at a fraction of the pace of a senior and relies on direct 1-1 help, together with learning by observing others. This is quite difficult online and requires a lot of hand-holding which most mid-level / seniors are not willing to do.
So saying that WFH policies should be the norm is no longer an acceptable statement. It sacrifices the longevity of the team and the company if juniors cannot be onboarded quickly.