Yet react 19 is almost (except for some edge cases that only affect very specific stuff) fully compatible with version 1. Try running a rails 3 app on rails 8 or vice versa.

The React versioning is a bit silly, but React 15 was the first major version (in 2016) which makes it more like 4 major releases in 9 years. Not that different from 8 major releases over 20 years.