R is not constantly breaking. R Core does a remarkable job ensuring backwards compatibility. There are only a few prominent examples of significant "breaking" behavior across decades of the language existing, and those can often be reverted by setting an option (e.g. `options(stringsAsFactors = TRUE)`). But backwards compatibility is the primary concern with any update to the R language or the packages maintained by R Core.

Now, if you're thinking about changes introduced by a specific user-contributed package breaking your analysis, that can indeed be a problem. But that can't be blamed on the R language. And the main user-contributed R statistics packages that have been around for decades (such as lme4 or survival) are mature and stable.