This. I almost see an anti-correlation, where the worst UX sites spend the most on UX designers -- I find FB and Quora a pain to use, while the easiest sites are the hacked-together bootstrap ones or the ones that never left the 90s.

Brief examples: Quora on mobile has the user-hostile floating headers and if I switch to desktop the text is impossibly small. FB takes a long time to load on comments I click from my notifications, and recently forced the switchover to the ugly redesign.