Some pre-89 code won't even compile today without putting in considerable effort.
Morris worm was the first widely know C exploit, which still gives us about 30 years of exploits to look into.
Regarding how many exploits other languages have, for starters not memory corruption due to out of bounds access, integer overflow or implicit casts, as Algol derived system languages, since 1961 (8 years before C was even an idea), had checks for those kind of errors.
C only made it to fame, because original UNIX could not be sold and its source code tapes went from university to university.
Had it not been so, probably we would be using Bliss, PL/I, Mesa, PL/S, and not having arguments how good one needs to be to write code that doesn't allow for memory corruption errors.
Exploits being consistently discovered over a long time is, and does help your argument.
Here's one for how safe that was: alloca could not guarantee the pointer it handed you is either valid, or the size you requested.
POSIX.1 only came along in '88 (with our first definition of stdlib). Whilst IO had mostly stabilised by that point, there were still plenty of platforms that didn't use the Bells header (stdio.h).
Files, signals, floating point behaviour, process creation - none of that was standardised yet.
Most of what was defined by POSIX already existed on common platforms, like SunOS, before it was formally standardized. SunOS 4.0 even had mmap in early 1988! (See https://archive.org/stream/bitsavers_sunsunos4.erenceManual1... )
>People who understand these essential basics, e.g. by starting with Asm, are going to be far less likely to make these sorts of mistakes and write less buggy code in general.
Userbinator's post continues and seems to paint the ecosystem as getting worse over time, as if it were much better in this area in the past. Pjmlp's point was that even the original C users who came from assembly, who were presumably more familiar with the essential basics of assembly and memory management, still pumped out vulnerable code as we see today. It doesn't seem like having a userbase made up of experienced assembly programmers is enough for C to be predictably safe.