So, I'm working out my own calculus. Delta Reserve+$75k spend gets Gold+blank check lounge access before accounting for any flying, at least for the moment. If the cards weren't otherwise so weak, that'd be a slam dunk. Platinum becomes workable (on paper, at least) - either $5k more in MQD spend, $50k more in CC spend, or another card (or two) yielding $2500 MQD. A Plat in a sock drawer is a valid option here.

The $13k gap between Plat and Diamond is just a dog that won't hunt at this time. The 10:1 spend ratio, wimpy MQD earn via DL's portal(s), and so on just...doesn't make that work.

In the meantime I'm trying to sort where I'll land over at AA/BA vis-a-vis this. I've got a year or so to actually make a decision (I'm burning a RUC on a flight in a week or two in order to take care of the extra year-o-status), so I'm giving AA a shot while I have that (DL was about a week too slow on the back-off).