1. React is 11 years old. Even "modern" React with hooks and such is more than 5 years old.
2. Express has been the backend server for Node for over a decade and it hasn't had a breaking semver change in 7 or 8 years.
The front end bundler ecosystem has been a hot mess forever though.
Compare this to Android which somehow manages to break its build system ~every few hours~ at least once per year.