And global warming was much milder when we had more pirates in the world [1]. Correlation is not causation. In the same period, YouTube's management style and public-facing attitude have changed dramatically, Google's general attempt at being the "good guys" has pretty much vanished, and beancounting has taken over as the guiding principle in many respects. I have zero reason to believe that had Adblocking not been a thing, there would have been any significant difference in the frequency or intrusiveness of the ads YouTube shows.
I wouldn't call them "milder". They weren't static ads. They were video ads. Often loud and un-skippable for a certain small amount of time. This is definitely equivalent to a "punch the monkey" ad.