TeX/LaTeX is a rich ecosystem that has grown over a long time. Over the last couple of years, pdftex, xetex and luatex have coexisted and pdftex was the stable

TeX/LaTeX is a rich ecosystem that has grown over a long time. Over the last couple of years, pdftex, xetex and luatex have coexisted and pdftex was the stable choice and the other two were functional but in beta stage. In the last years, xe and luatex became stable and pdftex entered maintenance mode. WYSIWYG is an antithesis to LaTeX, but I'm sure it's possible to base something like SwiftLaTeX on luatex instead of pdftex. This has changed only in the last few years. You listed a few requirements, and while many are achievable using pdftex, only lualatex tikz all the boxes. * unicode out of the box * otf font support * unicode in bib via biber / biblatex * easy extensibility by writing lua instead of plain tex there is more. But only because luatex is out of beta, does not mean pdftex suddenly stops working or needs to be deprecated.