Delta went the way of AA and you can use the credit card exclusively for status if you have the spend.

A Delta Reserve gets you 2,500 MQD for holding the card, plus 10% of the spend as MQD. If you have the ability to direct a lot of spend, you can flexibly top off your other sources of MQD to qualify for Diamond. Once you back out the value of the miles earned for the spend, it's something like $0.10 per qualifying dollar to manufacture, which is much cheaper than other non-organic routes.