For some reason, these instructions aren’t clear enough. First, you have to know whether or not you are using npm or yarn here, which is somewhat confusing. If you don’t know, you can try both.
npm uninstall -g create-react-app
yarn global remove create-react-app
However, I found that didn’t actually fix the issue when the package was cached, so to solve this you additionally need to also
npx clear-npx-cache to proceed