I've tried to move toward this kind of arrangement in the past, but have never quite broken through. While I'm fluent in HTML/CSS, the major obstacle to actually committing code as a UX/UI designer has been the codebase itself.

I can pop open a web inspector and make a bunch of changes, but that's the easy part. Unlike when I'm working on my own, far simpler side projects, I can't just switch over to VS Code and paste the changes in to the requisite selectors: Assuming I have a local environment set up (no easy feat itself!), now I have to track down React components, find their stylesheets, perhaps follow some leads out to other stylesheets coming from different libraries...

It's all something I'd love to get to a point of familiarity with in my next job (which I am currently looking for!), but the upfront time investment (in part by the developer to explain the repo to me) has kept it just out of reach so far.