It might be a decent time to look at other airlines and still protect your DL status, although I agree with the sentiment that the Big 3 are much more similar than they are different. I am still comfortable giving my business to DL when picking between the three. Price competition between them will always move my decision, but there has been little of that happening for the last few years.
I have tried it several times. I was a big AIrTran flyer after their rebirth in 1999 and loved their FF program. I also flew Northwest heavily, even getting to 1mm in their program. I tried TWA when they set up their Atlanta minihub. Air South — I was on them in the middle of a day trip on a free FF ticket ATL-JAX the day the airline folded; DL got me home. Alaska using a status match (a miniature Delta). Southwest after they purchased AIrTran. And MaxJet and then SilverJet to London. And some other misadventures.
Sticking out the ragged end of the COVID period on Delta. They urgently need to fix their manning levels on the phones. Yes, I think the snack box sucks, but I like the minican Old Fashioned. I have never cared about the duvet covers, plastic “suite” doorways, etc. Any flat seat is a rare blessing and I cannot bring myself to complain about the minute differences between them.