but it doesn't seem to happen the same way in other parts of the programming world. Even in Django, yes, there are squillions of libraries for different things, and many of them haven't been updated in years, but the long-lived ones don't tend to have breaking changes in (at least in my experience). It just seems to be front-end stuff where people will make breaking changes in some long-lived package, and for no obvious reason.

Make a new package, or a distinctly different version of the original package that won't get imported by a simple upgrade.

Or am I missing some reason that it's not as simple to do this in front-end stuff as it is in other areas?