the blog post inside the linked blog post goes over some points. each point is copy and pasted more or less.

• like for example the multiple times I've spent dozens of hours debugging a single issue only for it to turn out a small typo or a careless mistake that any language would catch at compile time, except for C
• Memory safety issues arising from the absolute lack of any documentation whatsoever of wlroots have also been quite the annoyance
• The development of a display server is very complicated, as they are very broad and complex pieces of software. Mixing a C library with 0 documentation is basically asking for trouble.
• new wayland features that require changes in wlroots tend to take ages to get merged into wlroots, like for example tearing, where a basically ready MR took 9 months to merge
• explicit sync still not being a thing, despite KDE and Gnome having implementations already (I believe it is now, but not at the time of the blog post)

https://www.youtube.com/watch?v=HhZ_HnqkJoo

this doesn't apply here. hyprland has announced that "all your wlroots programs will still work". so they are keeping support for wlr protcols

Hyprland never used wlroots itself. It always used a fork of it.