Wil Gomez has a list of why the last Mac Pro was better than the current Mac Pro and what the next Mac Pro really needs:
The second professional level Mac would be the Mac Pro Apple is working on now; the one we should expect next year, but Apple said it wouldn’t ship this year. But it could be 2019. Regardless, any modular Mac Pro will remain a very expensive device. The 2013 Mac Pro was recently upgraded to a 6-core, dual GPU version with a measly 16GB of RAM and a paltry 256GB of SSD storage. That’s hardly professional level. Apple’s own build-to-order specifications can get the Mac Pro up to 64GB of RAM, 1TB of SSD storage, 6GB dual GPUs, and a 12-core Xeon CPU for $6,999.
Expensive. That might explain why many so-called professional level Mac users moved to Windows or settled for a lesser iMac or MacBook Pro.