WFH absolutely screws over younger people joining an industry. There's nothing like face-to-face learning, and I don't envy anyone who's had to start their career recently.
Some companies do actually have explicit "new grad hire" cohorts with additional onboarding support targeted at new grads -- eg a seminar series or dedicated networking events.
Sometimes it's less formal or there's even no structured support at all.
But, in any case, I'm referring to companies that hire enough new grads each year to have an entirely separate recruiting mechanism for that population. When that's the case, it's just more likely that people are being hired as generic candidates rather than onto particular teams. And when that happens it's easier for people to fall through the cracks, because the direct manager didn't specifically pick that person as a good match for their specific need.
Mentoring remotely is definitely a skill that us older workers had to be intentional about cultivating in ourselves. The moment pandemic started, I bought a top-of-the-line iPad for whiteboarding, insisted my new hire mentors get the same from the company, and called up a couple old professors to get all their tips on remote teaching.
Hopefully the next generation will have it easier; their mentors experienced remote learning so might be better equipped for remote teaching/mentoring.