It's just about applying the existing communication technology and having policies that support mentorship or these other things that are supposedly impossible to do without being in person.
I believe that most of these supposedly intractable problems can be solved with a Discord/Matrix/IRC whatever and just enforcing policies about communication. Have a bi-weekly required five minute voice chat and at least one hour of time per day where people need to have the chat open. If juniors are not asking questions or seniors are not replying within X hours or whatever follow-up sessions from the five minute intro discussions is appropriate, then they get warned, and if the lack of communication effort continues, fired. And you make that policy clear.
You can also look into various types of 'multiplayer' virtual presence. Several different browser based or 2d or 3d (even VR) options for this.
I feel like people just stop trying to communicate more than a weekly meeting or something a lot of times when they are remote. That in no way proves that different types of communication or mentorship or whatever require face-to-face. People just need to show up online to communicate.
It can't be fixed industry wide. I guess it could be partially fixed at individual companies. But those are just band aids. It's just how it is. If you're not face to face, the relationships will be at arms length.
In addition to the mentorship issue, think about promotions. Especially to more senior levels. The people in the office or with pre-existing relationships will be the ones getting promoted and will be the power brokers. If you are someone who doesn't think that will be true, then (IMO) you are confusing how you wish the world to be for how the world is.
