Just a crazy idea, but could it be that they don't dogfood their own stuff? I have Ublock Origin Lite on by default (RIP full Ublock Origin) and a lot of sites look clean. I'm often not even aware that if I send a link to an article via Whatsapp or whatever, it may reflect badly on me that I send such an ad-overloaded mess to them. I just don't know the mess is there except sometimes by accident.

I watched someone getting a livestream of an important (to them) soccer game going via the sort of thing usually reserved for "adult" content - that any given click, be it "play" or "fullscreen" or whatever, has a 9/10 chance of triggering a junk popup rather than the intended action, so you play whack-a-mole until you finally get it playing, whack-a-mole again until you get fullscreen, and then for heaven's sake don't touch it any more. Whereas with the adblocker, typically it looks completely clean, with no junk popups, and every click doing exactly what it should on the first try.

Anyway so could it be that the web having turned into such ad-overloaded garbage, that even its designers have adblockers running and don't even fully realize what a mess they're publishing?