tl;dr: remedial classes are good and some schools are good at them. Admissions question aside, it's not a bad idea to get good at them.
I attended community college in my hometown, as well as a university elsewhere, and eventually completed my undergraduate education.
While I attended the community college, which openly advertises that it has no admissions requirements at all, I also worked there as a tutor in math. Since it had no entry requirements, the school had decent placement tests and a pretty damn comprehensive suite of remedial math courses. Some of the students I tutored were studying arithmetic (negative numbers, exponentiation), and some were even practicing how to pronounce and write out numbers by name in English and map those to Arabic numerals. There was no amount of ignorance that could make you unteachable there, as far as I could tell; you just had to find the right course.
Their math classes also included stuff you'd normally take at a university: when I was there, I took first-order logic, differential and integral calculus, vector calculus, systems of differential equations, statistics, discrete math, and probably some others I didn't take or forgot about. Some of those courses I had to retake at university anyway because of transfer credit limits and things like that, and in some of those cases, the community college version was actually better anyway (the university ones were fine).
I think it's awesome that the school had really weak admissions and really strong placement, and that it can take an earnest and reasonably intelligent high school dropout from the basics they missed all the way to being ready to dive into upper-division, in-major courses in STEM at a university.
It seems like that's an unspoken possibility for universities, too. Round out the catalogue, beef up placement exam regimes, further partnerships with local community colleges, lean into early exams and pre-tests within courses, and when students prove to be really unprepared, direct them to an appropriate class. It's not a matter of "waste 4 years just to not be able to graduate", it's "okay, it's going to take you longer to graduate because you have to take this detour in this subject area, so here's what your path now looks like". And of course dropping out or trying and failing are still (painful! expensive!) options, as they always were.
I'm not saying this is easy or cheap or a responsibility I expect universities to want. But "teach students the thing" can be a much saner option than the article seems to describe, which is hijacking existing courses that are purportedly focused on something else in order to teach their prerequisites inline.