That seems like it could work, and I would love to say you're right, but many of the companies advertising—especially as we're seeing more and more of the big players—have a really diverse ad spend budget so their dollars are all over the place. Because so many ads aren't looking for a direct sale but rather increase your awareness when you DO want to buy, say, laundry detergent, there's no way to tie your purchase to having seen an ad (though marketers LOVE to try and draw lines to efforts, many are hazy at best). So seeing ads and consciously not buying what you're seeing could in theory lead to a dip in sales, but the watch numbers are high, so no adveriser would be able to tell that dip is because of youtube, or podcasts or... uh... radio?.

So sadly the best way to hurt the system is to a) keep blocking the ads so the watch level is low and the advertisers want out or b) drop the watch level naturally by picking another platform.

Source: a lot of time in advertising.