I’ve been doing LaTeX for some major portion of its life and I’ve see so many “LaTeX killers” come and go. But my documents from 25 years ago still compile and render.
Yeah, remember Lout? That was all the rage, briefly, about twenty years ago.
Wow, I was initially very enthusiastic about lout, and I still think it had some good ideas. I just remember the templates not being as easily hacked/tweaked as (La)TeX, and the advice was generally "accept how it already works" when people asked how to adjust things. Not a good sign. Also I remember--at least I think I do--that the source files had arbitrary f01.c f02.c f03.c names, so it was hard to guess where anything was. That was strange.
That's been my experience; either it's a beautiful template that does almost everything you ever wanted, but if you want that last 1-5%, you're doomed, or it's just another LaTeX-style tool that may be objectively better in some way, but it's fighting against 25+ years of experience getting LaTeX to do exactly what I want it to do (and providing quite sane defaults when I don't care).