pigged
There is nothing wrong with mathematics and it is certainly not reserved for "the elite" whatever that is supposed to mean.
Convention is irrelevant except to ensure other people familiar with the convention can easily know what you're talking about. For programmers it is especially irrelevant as we usually only care about finding solutions to problems.
Correctness does not "only exist in the framework itself". If I ask you "if there are 6 people in the room, is it possible that among them there is no group of 3 which know each other and no group of 3 which don't know each other" the only correct answer is "no". The fact that this concept has a name in mathematics does not make the answer "no" any less correct.
Dismissing the importance of mathematics because you somehow find it "elitist" is anti-intellectualism at its worst.
So in the real world, this is what causes me problems - actual problems with a large application that cause friction with clients - people being bad at programming and not knowing even the most basic computer science and math, mostly manifesting itself in the application becoming littered with inefficient code over time (the second most common problem being lack of or superficial technical knowledge, such as using a framework or even language without understanding how it works under the hood, this usually manifests itself in the same way).
Note that the "I don't need to know math/cs" people will often not realize they needed something because they will just solve the problem incorrectly, inefficiently, or decide it is not possible to solve efficiently and compromise on requirements. What's worse, even if they are shown the error of their ways multiple times, they almost never truly change their mind, regardless of evidence. It is a mindset people seem to commit to early in their career, or even to a more general version of the same mindset in childhood, and never change it. That's why there's so many of them.
Sure, there might be situations where it is not useful to be a better programmer than you are. But I would say that is not the norm. I don't work on some algorithmically-super-complex application, it is just a typical large application used by professionals for their work; it doesn't involve any truly difficult problems but has a huge number of relatively small and easy problems all over the place. I'd say it's somewhere in the middle of the software development spectrum.
And I don't see why you think the average programmer knows less about the law than someone in another non-legal profession. In my experience this is simply not the case, and yes, reading about it on the internet is better than not reading about it at all. It's not like dentists spend their time reading actual law books. Honestly, I have no idea where you get this from, it sounds absolutely wrong, but I guess we'll have to agree to disagree on this.
I think the reality is the opposite of what you suggest, programmers are in no way an example of a profession where most practitioners have a deep and extensive knowledge. For most programmers, the learning method is finding out how to DO things (as in, find an example on the internet, try it, it works, I'm done) without actually understanding anything.
You must be very lucky in where you work if you think programmers know a lot of math and even know what "category theory" is.