For average consumers it's great. I think my phone is the only thing I own that could use 3.1(I assume, I've never looked because I do most everything wireless).
Almost everything (Including my 200Wh solar generator!) Will charge from 5v at 5W on a regular USB, and almost nothing really needs more than that, slow charging is quite often fine for phones and tablets.
Phones tell you if they slow charge, so it's just a matter of keeping the good cable plugged in the good adapter.
For the way most people use USB-C, as a power cable that can do data with a little extra work when needed, it's already great.