Thinking about this at a higher level, the real problem is that we use C arrays at all. But we can't stop using C arrays, because libc and a huge body of other C libraries out there represent lists of data using C arrays.

As a useful counterexample, glib has GArray, GPtrArray, and GList, along with functions that you use to manipulate the lists. Those functions are presumably implemented correctly, and will prevent you from making out-of-bounds accesses.

But of course those things are not widely adopted, because they're not standardized, they're not in libc, and libc has not been reimagined such that all of its APIs take and return these safer list primitives instead of bare C arrays.

(And sure, GArray etc. are not necessarily suitable everywhere, as they require heap allocations. But I could imagine a safe abstraction that could allow for using stack or static allocations to back it.)

So I see something like Checked C as a band-aid, when the language and stdlib just needs a complete overhaul. Obviously that's incredibly unlikely to ever happen, so something like Checked C is a decent compromise, I guess.