I had a very well organized and documented remote onboarding experience. There was a list of meetings to schedule with the names of the relevant people and tasks to undertake, as well as a dedicated mentor that you met with as often as you'd like. At the end you met with at least one person on each team and got lots of time with your own team while they explained the systems to you.

Of course this is at a company that was remote before the pandemic.

I just wrote a sample of our onboarding process in another comment, and it sounds similar. And yes, we were remote pre-covid.

When a person signs in the first day, they already have a bunch of meetings scheduled (meet and greets, explainers, etc...), some work assigned (I like to have a bit of a goal when exploring a new code base, but this work isn't expected to get done right away), etc...

It can be done well, but takes some thinking through.