The only old platform is the WK2, and as I mentioned earlier in the thread, Mercedes is also still using their version of it (W166), so I'm not sure that's really a valid criticism. It was/is an excellent platform (we've owned 4x WK2 vehicles) and its replacement (WL) doesn't have an SRT offering for example and has very different driving dynamics.
Yes, it should have gotten more than the 200 and Pacifica. It used to get more upscale versions of platforms, like the Aspen, 300, Town and Country. I think the writing was on the wall when the only thing it got after the 200 was Pacifica, seemingly as a test of whether they were able to move a whole new style of minivan.
My understanding of what drove this was that Jeep was easier to push up market as a marque, while Chrysler floundered with the 300, unable to really get into that space. It naturally became viewed as offering more upscale products than Dodge and people wanted SUV's, hence, Wagoneer/Grand Wagoneer and all the various trims of Grand Cherokee with similar options and materials as to what you find in a Benz or Bimmer.
My understanding is that they really are (new leadership) trying to make something worthwhile and suitable of the nameplate with the new Charger/Challenger. I'm sure the Durango will eventually get a platform upgrade, but if you look at the DS trucks, they had to continue to sell the platform (RAM Classic) because the demand was there and they'd be foolish not to capitalize on it and perhaps there are challenges with the WL and the larger 6.4 and 6.2L engines (as they are still making Durango Hellcat) that aren't present on the WK2?