I suspect most people refer to credit card churning and manufactured spending when it comes to playing the "miles game". This is actually a fairly small subset of the flying public and I doubt DL really misses those types of flyers that much. The current DL program is now closer to the WN/B6 revenue based programs than traditional legacy programs. Note those airlines also don't seem to have much problem in attracting flyers in spite of their programs being revenue based. For most flyers, the mileage program is just one factor among many for why they choose an airline.

If you frequent this forum regularly, you can find the occasional DL D1 award unicorns/outliers at times -- like the current springtime US-EU D1 award sale available for flights on/before May 8th (which has been going on for several weeks now).