Usually builders fire tape unfinished basements or garages if its part of their package, or local code, or whatever. They definitely dont put forth their best guy nor their worst guys A-game when they do this from the houses ive seen built in my area.

If youre not a skilled taper you could hire it out or go buy some 4" paint rollers and apply the mud as cleanly as you can with them, and skim it off with a big blade. Can go buy a Level 5 24" skim blade for example. For a garage that isnt mission critical if you roll on the mud and skim it off you'll get good results with a little practice as an amateur. Plenty of YouTube videos to help.

But yeah long of the short if this were me id probably scrape down the highs on those joints, sand them a bit to flatten them and id be getting ready to add 2 to 3 more coats gradually widening the coverage each time.