I have been Platinum or Diamond with Delta for well over two decades, and I am not a hub captive. They have been good to me when I have to change flights at the last minute, even if it is not their fault. Their planes are typically good and are on the high end of airline IFE systems. FAs and GAs at many stations are consistently capable and friendly, although knowledge of some phone agents (even at the Diamond line) is suffering a bit lately. Upgrades to First used to be very common; much less so now, but that is not just an issue for Delta. I have started to diversify the airlines I fly with based on price and schedule (this year Delta is half of my flying, rather than 90% in the past), and AA and UA so far have failed to impress me. WN is a lot better but has its obvious drawbacks too. So, I still often end up with Delta, not so much because of a sense of loyalty or because they do so much for me but because they have a good product and price relative to the competition.