WTF is up with DMPs? CPMs of First Party Data & Viewability

The premise of this blog post is that DMPs on the demand side are supposed to identify higher performing inventory and suggest higher bids for it. This also means devaluing junk inventory.

If that is the case, why are we having discussions about viewable impressions? Wouldn't  non viewable impressions have poor performance and thereby the DMP would bid lower to nothing on it? If DMPs are doing their job, wouldn't the market identify the bad players and take care of it through pricing?

At the Digiday WTF Programmatic Conference last week I had a conversation with a publisher who complained that packages assembled with first party data and offered as a PMP were not getting the higher CPMs that they deserved. He said they deserved the higher CPMs based on the lift in performance they provided versus inventory without the first party data. Again, shouldn't the DMP recognize the lift and bid higher for the inventory with deterministic data?

What am I missing here? Is the value of the DMP a myth? If they are not determining pricing based on performance, then what kind of job are they doing on assumptive data?