Same thing happened to us in Memphis - I used to could fly almost anywhere non-stop - now a stop in Atlanta is required - why Delta maintains hubs in both MSP and Detroit I will never understand...
Having said that, we have had terrific luck with American Airlines through CLT - about half the price of Delta and good schedules (though not perfect - nine hour layover in MIA last year) - we used to be all Delta all the time - but AA has our attention now