I actually have really enjoyed SiLE[0] as a replacement. The only caveat being that it has no where near the ecosystem that LaTeX has built up over the years. I do think that it is better under the hood than LaTeX though and much easier to customize. [0]: https://sile-typesetter.org/
This is interesting. I tried out SILE as a LaTeX alternative a few months ago and I had many more issues with it (kerning, line spacing) than with LaTeX. Perhaps it has gotten better in that while? (Or perhaps I am just dense and I wasn't doing something right)