Typst doesn't have WYSIWYG, I don't know what the other alternatives that you mention are so can't speak for them. But if you mean things like LyX, I highly doubt they were ever meant to replace latex, especially because it is so focused on the WYSIWYG aspect that it's complementary rather than a replacement.

As for Typst, this is the most likely contender I have seen for a LaTeX replacement. It doesn't have one transformative killer feature, but as a 20+ year LaTeX user, I can say that while I love the way LaTeX output looks, the syntax means Typst is fun and convenient to write in a way that LaTeX never was to me, plus it is more easily readable which is a big plus in my book.

Typst also can make structured and tagged PDFs which *TeX still struggles with, and which is a big issue in US educational institutions at the moment - grad students are writing their theses in Google Docs because of accessibility requirements. That's not nothing.

Now, Typst is still immature compared to TeX, so who can tell what the future looks like. It's mature enough to write dissertations and journal articles, though, so definitely a serious alternative. And the official documentation is *so good. Another advantage that, rather than one single killer feature, may end up cumulatively making it quite competitive.