I personally visit "a great many websites" daily, and rarely have this problem. Maybe it's uBlock doing it's job, or maybe it's the kind of site you go to?
Of course it isn't. Pihole and similar DNS-based blockers do nothing for those kinds of spam which require performing DOM manipulations to be removed. Check uBlock settings after installing it. It has a separate "annoyances" list. I enabled everything in it a few years ago and never had a single problem. It removes all the GDPR banners, "please give us your email" popups, useless "oh I am so original" plates in forum signatures, etc. etc.
Pihole blocks server requests but ublock can do a whole lot more to the page by blocking specific html, css, and scripts. Ublock will prevent YouTube ads, for example, whereas pihole cannot as they come from the same server as the content.
