What kind of web dev can't handle React? Meanwhile, htmx uses clunky, non-standard attributes that rely on logic and templates that are split up in a million different places. Plus it requires a context switch to do anything client side.
I know so-called "senior frontend engineers" whose speciality is React, and who can't handle React. So all others...
This thing (and others like Vue, let me be clear) adds many layers of complexity over the web platform (client-side routing, data fetching, state management, rendering, etc.) and many third-party JS libs that you have to constantly update. You just can't say that it's standard/base web development.
Don't underestimate the learning commitment it takes to learn react. Learning the basics of react and its component architecture is one thing, learning all the tricks and gotchas related to hooks, accidental re-renders, accidental no-renders, etc takes time.
Throw in the usual pile of libraries used with any larger react app and it can easily take months to really get moving.