C is a very slow moving language, but platform-specific APIs (meaning outside of stdlib) change more frequently. "C" does not exist in isolation, and outside of toy applications, not useful without the underlying platform APIs. If you were migrating C code, from say, Mac OS 7, or even Mac OS X 10.1, you would have to make many, many changes. If you're migrating code across Unix platforms (say, 1990's SunOS to modern Linux), you'll require changes, too.
sure, but the gratuitous breakage i'm complaining about in python is inside of stdlib, and even in the language syntax itself. and i've frequently taken c code from 1990s sunos and compiled it on modern linux, and yes, it's true that it usually requires a few changes where it interacts with the outside world—but only a few
it's true that very small programs are often little more than glue between the underlying platform apis, but large programs tend to have a much lower surface-to-volume ratio. that's why τεχ still runs, virtually unchanged since 01990, and you can easily render plain τεχ documents from the 80s or 90s with τεχ today—even with pdfτεχ
