Fedora's foundations meet proprietary drivers

Nouveau can't be counted on to work, as in at all. I'm running a completely ordinary nvidia card, a GT120 which is hardly new, and while it's been working with most of the recent 4.x kernels, there were several 3.x kernels which were completely unusable with nouveau (garbled screen).

So the "important functionality" that isn't reliably delivered by nouveau is the ability to use your machine for anything at all that involves the display.