The Colgan crew was hired into the airline environment at 250hrs. When you are building your time, you are really conditioning your reactions to airplane energy states. By entering the airline environment early (autopilot everywhere, going fast, IMC, heavy turbulence, night, complex mechanical problems) your energy state awareness and reactions are poorly trained.
Couple things here. First, you're not getting any actual training from 250 to 1500 hours. By then you have your certs and you're doing whatever you need to on your own to get to 1500 hours. You are just gaining experience. That's worth something, but it is not "training". Your training stays exactly the same over that time, and in fact you probably forget whatever training you're not actually specializing in to gain your hours. For example, if you are building time as a single engine CFI, you are going to forget a lot of your multi-engine training by the 1500 hour mark. Ditto for instrument training (vs. building time VFR), automation training (vs. hand flying), etc.
Second, the experience you're gaining is most likely going to be in the same type of plane you trained in, which will probably not have autopilot or even be a complex airplane with landing gear. This does depend on how you trained to begin with and what you end up doing to build your hours, but that just points out how poorly-considered the 1500 hour requirement is. Someone may come out of that with 1500 hours of complex, multi-engine, autopilot experience flying into Class B airports, while someone else may come out of it with 1500 hours of single engine, non-complex, 100% hand-flown experience flying into untowered Class E airports. The former may have some relevance to airline flying; the latter will not. Both will probably pass an ATP, but the latter has probably spent about 1250 hours doing busywork that has no relation to what he/she will be doing at an airline.
I'm not saying we should kill the reg and take pilots at 250 hours. What I am saying is that an extra 1250 hours hand-flying a single engine Cessna - which is all that the regs require - is not going to prepare you at all for flying an airliner. Taking pilots at 500 hours, if that second 250 hours was spent on actual training that's relevant for airline flying, would be safer and would help alleviate the pilot shortage, which has the potential in itself for making flying less safe by forcing airlines to take even the least qualified, most poorly performing pilots. Remove some of the barriers of entry and you may make the pilot profession more competitive again, so that only the best need be considered by the airlines.
This isn't 1960 and the industry isn't small enough anymore to be able to pick and choose its pilots. At the same time, the requirements have ballooned to where almost nobody can afford to become a pilot anymore, despite those requirements having nothing much to do with flying for the airlines. The question is how can you best ensure safety while also ensuring a steady supply of well-trained pilots? The current system is not doing it. At some point you're going to see an airline accident caused by a new-hire pilot with 1500 hours of single-engine flying who failed 5 checkrides over his training period but who the airline hired because they were just desperate for pilots, and then this debate's going to take on more urgency.
I'm tired of being a wanna-be league bowler. I wanna be a league bowler!