React Router v4 was released in was released in March 2017 (more than 8 years ago!). v5 was released in May 2019 with no API changes. v6 was released in November 2021 with a new API based on React hooks (this API was much better than the previous). v7 was released in November 2024 with the "Remix" APIs (most importantly the "framework mode"). So, the gaps are 4 years and 3 years - that's doesn't seem that crazy.

I personally updated Remix v2 project to React Router v7 and because I used various flags to prepare for the upgrade, it was done without any issue and fairly quickly.

> entire library in massive, backwards-incompatible ways ... EVERY. NEW. VERSION

So a new major version has some breaking changes? Why is that surprising?