Honestly I started straying earlier this year.....
Started using UA on DTW-DEN instead of DL. I could by an F ticket on UA for only slightly more than a Y ticket on DL (and came out ahead since I thus got free bags as I have no status on UA). Their schedule was superior as DL's last departure out of DEN to DTW was 3:30pm, and UA has a 6:30pm flight.

I've been tempted to start using G4 out of FNT to PIE instead of DL on DTW-TPA. I'm 30 minutes easy drive up to FNT versus the insane construction this summer on I-96, I-275, US-23 driving to DTW this summer and my family in Florida is really close to PIE.

If the best I can do in the new era is a SM/GM which the benefits are silly and I can just get by doing WFBF, whats the point. Just go free-agent and go ULCC where it makes sense or WFBF on the legacies where it makes sense.

Not to mention, DL has gutted the schedule into so many smaller markets these days, its easier to drive sometimes, or just fly to the closest major city nonstop and rent a car. Most those major cities have another carrier on the route from DTW.