I think the UX issues you’re describing are less related to culture changes in companies and more just in the industry in general

UX are designed by and for people who don’t really use computers. They use mobile devices and tablets

It’s an industry wide phenomenon

You are onto something there, if you mean, the design roles being taken over by the people who are not techies - like the POs. But if you just refer to UX being designed for mobile devices - that is not an excuse for an even worse UX on the mobile. If anything I would have expected more effort put in there, given how many more issues the limited screen estate can cause...