Come on, man. "There were three units (and 5 more that that I personally never used and didn't realize were critical for proper print.css stylesheets because I never printed anything). Today there are 18! A six-fold increase"

You mean two-fold. Hyperbole doesn't work when you're flat out lying about the numbers with the evidence for that lie in the same sentence.

And how many of those 18 are commonly used? Because it's not "all of them", not everything on the web needs all of them (a web page doesn't need physical dimensions, an app doesn't need pixels, you don't use every unit for everythi9ng).

Complaining about "what it can do" when you don't use what it can do doesn't make a whole lot of sense. Learn what you need to use, ignore the parts you don't need. Learn those through trivia and incidental "oh huh I didn't know that" moments.