I completely agree. In fact, I believe URL design should be part of UX design, and although I've worked with 30+ UX designers, I've never once received guidance on URLs.
We all are trying to understand a problem and trying to figure out the best solution.
How each role approaches this has some low level specializations but high level learnings can be shared.
I can imagine in your situation as a pure designer how you got it though though, sorry to hear that and I wish other devs cared more. I've def mentoring people to care about it so hope others do so too.