"just how many people are fucking terrible at their jobs".

Apparently so. When I review mathematics software it's clear that non-mathematicians have no clue what they are doing. Many of them are subtlely broken, they use either trivial algorithms or extremely inefficient implementations of sophisticated algorithms (e.g trial division tends to be the most efficient factorization algorithm because they can't implement anything else efficiently or correctly).

The only difference I've noticed with the rise of LLM coding is that more exotic functions tend to be implemented, completely ignoring it's applicability. e.g using the Riemann Zeta function to prove primality of an integer, even though this is both very inefficient and floating-point accuracy renders it useless for nearly all 64-bit integers.