Sponsors don't pay a fixed amount to creators. They pay for (estimated) views.
What I'm proposing is exactly, 100% symmetric to how advertisers who pay Google for YouTube ad placement are already treated -- they pay for views, and YouTube can and does choose to not show those ads to some users, those who pay for Premium. Is that unfair for the ad buyers? Sure, if you squint right… but they're not being deprived something they paid for, they're just not being offered the option to put in ads in front of that particular market.
Before Youtube Premium, I would have said the same thing about blocking first-party ads in YouTube. It was weird they didn't do that thing. And then they did it. So now it's not weird I guess?