React components built as div soup may actually be worse for accessibility than thoughtfully written no-JS HTML.
My take is that it's the growing complexity of web development (yes, React has some responsibility here), combined with the constant influx of new developers, that's largely to blame for any overall proportional loss in the practice of accessible markup.
If a React dev leans on an accessible UI framework like Chakra, or Headless UI, or React-Aria, they're probably better off from an accessibility perspective than a dev that tries to implement WAI guidelines from scratch.