Sure, there is a small set of people who choose not to run JS, or use something like lynx that doesn't support it, but almost every browser version released in the last 20 years, certainly all the graphical ones, have by default good enough JS support to gather basic statistics and send them back to the server.
Near-universal: not universal. But people still running very old devices or browsers are not going to have a fun time on many sites regardless, and WebGPU is not likely to be used casually on random sites: it will be used for the same stuff that WebGL and canvas is today: mostly for special-purpose things like games, some visualisations, etc. – the sort of stuff that very old and slow devices will have trouble with in the first place.
So for fingerprinting, got it.
According to caniuse, promises are supported by Chrome since v33, by Edge since v12, by Firefox since v29, and by Safari since 7.1.
Both Chrome 33 and Firefox 29 were released in 2014.