I had a different path to the flight deck than most. I did some single pilot aerial survey in a 172, nearly 2,000 hours of various VFR shenanigans in Alaska, and then 850 hours single pilot, hand flown IFR in a Navajo in the Rockies. I'll spare you all the war stories, but I'd like to think I learned a few things.
I'll never forget one of my first times in "mountainous" terrain in 121 ops, flying the Dash 8 with a checkairman in the left seat into ROA, clear day, visual approach. I could tell this guy was really nervous handing the controls over to a "green" FO in that environment. Sure, I was new to the airplane, but the tried and true combinations of pitch, power, airspeed, and eyeball, airplane, runway will get the job done whenever you can actually apply them.
I was never an instructor, but I'd like to think the art of teaching a student while keeping the both of you alive has some practical application to CRM in a flight deck. I'll let those with more experience in that arena opine.
So here's the thing: I would say it's absolutely true that the more experience one has in a variety of situations, the better off one will be. But one of the problems that we're facing is there are fewer of those experience building jobs to go around, which has implications both to what kind of experience people have when they strap into a 121 aircraft, AND how many people can be in the pipeline at any given time to fill those positions. There are only so many aerial survey, night freight, jet charter, etc, etc, jobs to go around, while the need at the 121 carriers will continue to grow unabated.
I'm all for having very high barriers to entry in this profession for both safety and economic reasons, and for that reason I hope the ATP rule doesn't change for a long time. But I'm pretty sure that it's going to change at some point.
What does it change to? Well that's the million dollar question.