There are tons of people who are perfectly proficient in CSS who are not won over to utility classes. As you become more won over, you start writing files full of utility classes that… wait for it… someone else has already written! With huge coverage over CSS! And really good defaults! And lots of escape hatches!
And to top it off, nothing guarantees your colleagues are actually going to use those instead of creating their own ad hoc “semantic CSS” or whatever their preference is.
If you decide you’re a utility-only frontend, then… there’s a great tool for that!
So now why on earth are you still plugging away at that utils.css?