Delta will hire people all sorts of backgrounds, lower time, high time, corporate, cargo, military. FAA violations, terminations, etc. It's all about how you approach and discuss it in the interview because think they want someone who shows maturity, takes responsibly for their choices in life and isn't trying to hide anything.

If someone stayed at a regional for 15 years when hiring opportunities and other places came and went, but said, "well, yes, I could of come to Delta 8 years ago but I was raising my kids/caring for a sick relative/financially couldn't make the jump/had other things I was doing but now I feel that I'm ready. I do bring good experience and some seasoning for my years flying the CRJ. I flew into many of Delat's hub airports but also did non-tower operations into small cities, which I think is a great variety of experience to bring to Delta" that answer will probably go over well.

If he said, "well, I didn't come to Delta 8 years ago because I didn't want to jerk gear for some 35 year old Captain who was my FO years ago. But now my regional looks to be on the rocks and basically I need another job, so I figured I'd try Delta. I mean, I've really been working for you at your wholly-owned regional forever. I'll fit right as an FO until I can upgrade again." it might be a different outcome in the interview.

It's all about how to respond to your background. No one is perfect - most everyone has something in their background that can be discussed at the interview. It's how you respond to it and explain it.