How does something so endemic like this get fixed?

That's a very good question. Ultimately, the standards of practice in traffic engineering need to change. Speaking of which: to put a finer point on just how much of an uphill battle that is, consider the fact that even the name itself^1^ -- "traffic engineering" -- is biased towards narrow concern for the routing of cars at the expense of holistic consideration of the street as a place. (See also: confessions #2, #20, and #28) There's a huge amount of institutional inertia supporting the bad status quo, including everything from university curriculum, to standards documents like the AASHTO Green Book and the MUTCD, to the fact that young Engineers-In-Training (EITs) are required to work under existing licensed Professional Engineers (PEs) for about half a decade (it varies depending on circumstances) before being allowed by law to strike out on their own -- which on balance is almost certainly a good thing because we definitely don't want unqualified people stamping plans, but also could lead to being inculcated into old ways of thinking and having latent new urbanist inclinations beaten out of them.

Fun fact: the biggest US traffic engineering research group, one which has an outsize influence in writing those standards documents, is none other than the Texas A&M Transportation Institute (TTI). In Texas. Not that there's anything wrong with that, but yea.

Anyway, one way for non-engineers to try to help that happen faster -- other than bitching about it on social media like I'm doing right now -- would be to educate yourself on New Urbanist/Strong Towns/Fuck Cars/etc. ideas, then get involved with your local politics and lobby for said ideas to be implemented. More concretely, read Jane Jacobs and Shoup and watch a bunch of Not Just Bikes videos, then call up your city councilperson, county commissioner and state rep, join whatever citizen planning groups happen to be around (e.g. my city has "NPUs"), and start bitching at those people about it. You can also go to public hearings for road projects and bitch at the engineers directly (they love that sort of thing, LOL).

^1^ It's a totally different subject -- albeit one I'm also passionate about -- but I like to cite this article as a good demonstration of how framing matters. It really can't just be dismissed as "mere semantics."