I work on way too many apps to pay much attention to any of them. I use Vuetify (a material design framework for VueJS) and it works beautifully.
Personally I think Development is becoming too idealistic. Ideally everything works for everyone all the time. But that's never the case, in my experience. These principles are a godsend for those of us who have bosses that want the app, "flashy", but also functional. While also having an abysmal amount of time to work on said app.
Personally I'd love to see less, "stop using this", and more, "start using this instead, here's why". I don't have time to go in and hack my material design framework, to fix an issue, I haven't had an issue with.
Read a book, and create your own UI doesn't work for me.
P.S. WCAG principles are basically unattainable in the real world. Almost any national entity has hundreds of millions of violations. I know because I also manage an app that scans for them.