I recently had the opposite experience. App was built in older version of React/MUI/CRA/tsc (project started in 2020). I upgraded everything to latest, removed CRA for vite, and it just worked for the most part (vite has some docs for upgrading from CRA). MUI had a few things deprecated, but it didn't break. Removed the yarn lock and switched everything over to vanilla npm now that it has package locks. Took < 1 hour.