They have been able to maintain quality and reliability at mainline because they have made the investments in the operation/people/infrastructure to do so.... It's hard to have reliable service when you squeeze your "partners" into money losing contracts and rebid flying/station/ground handling every 2 years while also creating your own alter-ego companies to bid against them.

While I agree that more mainline flying is beneficial to us all in the long run... The Delta, United, and Americans of the world can't just throw their hands up claiming ignorance of how this all happened. Pilot shortage is part of it, but the airlines themselves have played a huge part in this mess. The Wall St focus on quarterly results has led to a loss of long-term vision in my opinion.