Besides native UTF support and fonts what advantages do the XeLaTeX and LuaTeX ecosystems offer over LaTeX?
You mention writing a novella as your use case, but I don't think that's a particularly difficult task for a typesetting engine. If you found typesetting a textbook with "rich" margins, annotations, and figures significantnly easier I would be more inclined to learn about alternatives.
With LaTeX I can transform my research papers to comply with a publisher's template in a few lines of code. Sure there are some annoyances such as compile compile bibtex compile, but the ecosystem is mature enough that most of these are well handled.
You mention writing a novella as your use case, but I don't think that's a particularly difficult task for a typesetting engine. If you found typesetting a textbook with "rich" margins, annotations, and figures significantnly easier I would be more inclined to learn about alternatives.
With LaTeX I can transform my research papers to comply with a publisher's template in a few lines of code. Sure there are some annoyances such as compile compile bibtex compile, but the ecosystem is mature enough that most of these are well handled.