The problem is that mentoring only really works in a school or club environment or perhaps a well populated airfield.
Where mentoring doesn't work is for the pilot that gets their licence and goes off and does my own thing. I fell into that category, got my licence and had say 50 hours, bought a plane and went off and did my own thing. There was no club, limited flying mates and no real direction (until later on).
Aviation requires you to often hear things and interpret these things for yourself to gain exposure and experience. If you miss that, you miss out on a lot.