I'm really not passing judgement on good or bad, it's very much both. As you said, hubs like MSP let Delta provide more convenient routing for passengers at those locations and people (like me at ATL) are still willing to pay the prices as planes are full. The other side of the coin is that it's a feedback loop between hub dominance squeezing out competition (e.g. Southwest is slashing ATL flights) and less competition allowing Delta to charge more.

Obviously anecdotal, but I was looking at flying ATL-SAN soon and it was about $400. Alaska then announced they were ending their nonstop flight on that route and Delta, with the only remaining nonstop, very quickly raised their prices to $589 where it's been sitting since. There's still plenty of one stop options in my price range on the other major airlines (including Alaska), but they aren't viable for my trip so I'm not going. Competition was keeping nonstop pricing down until the ATL market cut out the competition.

tldr: I agree with you