It's so true, and it really bugs me considering the Mac Pro was, to my eye, a really cool concept that was about two years ahead of it's time. What it really needs is TB3 and, of course, the latest CPU/GPUs. Shipping a PCI TB3 dock to go with it would also be a fantastic idea, but there are some 3rd party options for that out there now.
It is just mind boggling what happened with that computer. So weird that it has just sat there for three years. And with the Mac Mini also sitting around and gimped, it creates such a hole in the lineup. It is the hole that has been there forever due to lack of the "headless" Mac. But Apple is just letting it get bigger and bigger. Crazy.