With an ender 3 it's easy enough, but it does not feel as nice as shot ABS plastic caps.

I am sure though, if you spent time polishing and painting the surface it would feel much better. It's still similar plastic after all.

Biggest problem for me, if printed in PLA the + shaped slot eventually gets too loose and the key pops off. Can just print another but it's annoying for sure.

Resin printers would likely have a much nicer out of the printer feel, with much smoother details at that size (for caps with 3D details on top). You could also print a whole set much quicker. Same speed for one cap as it would be for 100 at once.

I printed a few for a friend. They seem to work just fine, but if you look close you can see the ‘terraced’ steps in the printing. Probably feels a bit rough. I guess you could smooth that with acetone vapour and ABS filament if so inclined.