If you are happy with one version you can just stick to it?

You don't have to update your phone and laptop every year, even if you are made to feel so.

In our case we wanted to upgrade another dependency (react-admin) which necessitated a react-router upgrade, which we used throughout the rest of our application, so it was a reasonable amount of work and sticking to the old one was not an option.

I wish this were true. In the modern JavaScript ecosystem you either pin everything or pin nothing.

You do have to upgrade. At some point incompatibilities between libraries arise, and if neglected for too long at some point it becomes impossible to update everything. Keeping dependencies up to date is an important part of software maintenance.

Those breaking changes were especially painful in React Native apps. Thankfully there are some good alternatives now.

Would you mind sharing what are they?

You could take a look at these:

https://tanstack.com/router/latest

https://github.com/molefrog/wouter/

Wouter is great, I recommend.

...and completely changing how everything works on each major version change.

Take one more sir.