What in microtype makes "a big difference"? I don't recall using it (my LaTeX years are long behind me), but all of the examples on https://www.khirevich.com/latex/microtype/ seem incredibly minor. I don't think I'd notice any of them as the reader.
It is what sets professional typography apart. Only Adobe InDesign provides a comparable implementation, tweaking all those details.
See https://en.wikipedia.org/wiki/Hz-program for a better explanation and an example.
IMHO, the difference is obvious and not minor. Without microtypography texts look ugly: https://upload.wikimedia.org/wikipedia/commons/0/03/Hz_Progr...
Which is to say, half of these things are pretty subjective.
TeXmacs claims to have implemented microtypography as well (https://www.texmacs.org/tmweb/home/news.en.html, as I am reading it, in the opening paragraph on version 2.1)