I guess we will all read these lists through whatever “colored” glasses we choose to wear, but I like to see them more as “mosaics” of ALL the possible ways to a professional stage career - “big name” school or “no name” school; college or no college; BFA or BA or BM or BS or MFA; degree in MT or Acting or VP or Dance or Philosophy or Linguistics; born to a “Theater” family or an “Engineering” family. I think the one over-riding commonality is hard work and perseverance.
Based on “basic statistics” of the make up of any typical musical cast, I’m guessing that the majority of the names on these lists are ensemble and the majority of ensemble is generally “recently” out of college. I think it might be much more “telling” to find out what came “before” all those professional credits listed after the names of the more “mature” actors. They had “something” that made them successful. I’m betting more than any particular “named” training, it’s hard work, perseverance, willingness to learn and being able to “make nice” with colleagues.
Anyway, that’s what my glasses let me see.