I know it's possible to have workarounds and I have used them as needed. But the workarounds still have bugs, or are OS specific (your third one for instance),

I know it's possible to have workarounds and I have used them as needed. But the workarounds still have bugs, or are OS specific (your third one for instance), and they don't solve the problem of slow compilation. There are also fundamental limits to TeX language such as the number of arguments to a function limited to 9 [1], or overloading functions is a pain [2], etc etc. The advantage of rewriting from scratch in a modern language is that these issues can all be dealt with without workarounds. [1] https://tex.stackexchange.com/questions/2132/how-to-define-a-command-that-takes-more-than-9-arguments https://tex.stackexchange.com/questions/2132/how-to-define-a... [2] https://tex.stackexchange.com/questions/448877/check-number-of-arguments-in-a-command https://tex.stackexchange.com/questions/448877/check-number-...