Delta is infamous for changing flight times on us. I think the presence in DEN for Delta is very limited, unless we connect through ATL or SLC.
Same with American Airlines, limited presence, changed our flight times for a trip we had several times.
United has been consistently good for most of our flights to Maui.
We are attempting Southwest next May for a Maui trip. We will see how that goes. After flying first class for many years, it could be too economy for us, but we will be going with two grandkids, and one of them will be between us in the seats. I need to use our points and money we have been collecting. We just rarely fly even to Orlando from Denver. We drive most of our trips.