I'm not a programmer (unless we count shell and python), but out of all the "text editor" bobs on a desktop Geany really hits some kind of sweet spot, except for adding languages.
Your discussion here made me think of the text editor Joe, which has now been retired to AUR for some reason. It's complete and anyone can add a language with a syntax file. Joe itself has a stateful lexer that when given the right information can parse anything and understand what it means.
Granted, it hasn't been sincerely updated in well over a decade, but it's feature complete and has a nice CTags system. Unfortunately, that also means it doesn't support LSPs, which do seem to be supperior for some things.
My 2-cents :) I have created several state graphs for languages under Joe, and while it took some getting used to, the system itself doesn't have to change with the changing landscape, just add another syntax.