I have a similar experience with XeLaTeX. The "it's not unicode unless you jump through hoops" and "oh you want to use opentype fonts? I'm sorry to hear that" of plain LaTeX2e always make me go back to XeLaTeX instead.
You're still using (mostly the same) plain old LaTeX 2e with pdftex, xetex, and luatex (pdflatex, xelatex, and lualatex). Those are just 3 different engines for Knuth's original tex. As far as I know, some parts of all 3 are written in WEB (which is a language that persists mostly because Knuth's TeX is written in it).
Note that LaTeX2e is just a set of commands, a bunch of which are absolutely ridiculous to use in plain LaTeX, and simply not used when using LaTeX in conjunction with XeTeX as engine, because XeTeX can do things that plain TeX just can't, and so all the insanity that LaTeX2 had to invent to make TeX "do things it was never designed for" simply aren't used when you're writing XeLaTeX documents. Like everything being Unicode by default, no packages/macros/special affordances required. Including not needing stuff like \hat{...} or \grave{...} because those make no sense when everything's Unicode: just write text. Or having direct font access instead of needing to go through the horrendously outdated TeX font metric concept.
While what you're saying is true, I get the feeling that you want to say that this is in contrast to LaTeX3, which isn't "plain old LaTeX 2e". Except... that it is. The project to have a new engine has been scrapped a long time ago. LaTeX3 is just another layer above LaTeX 2e. With all its cruft.
