You can use Typst 100% for free, just like LaTeX. There's a CLI for compilation, there's an LSP, code formatter, etc. Complaining that the web app has a paid tier is like complaining that Overleaf is paid.
As for why people shill Typst over LaTeX, it's just a better overall experience. Things that are annoying in LaTeX are easy in Typst. I've written plenty of LaTeX for academic papers and my Master's dissertation, but I'm now writing my PhD thesis in Typst. It's so much better. The only barrier to using it everywhere is that my colleagues still prefer to use Overleaf for collaboration, which forces me to use LaTeX for papers.
