I'd say that the more accurate version of that premise is that people will exert some limited amount of effort in order to avoid ads (or fees, for that matter), and the challenge for the service provider is to make blocking ads more annoying than simply paying the fee. The real question is how successful Google will actually be at that, and that is admittedly a bit of an open question. That said, we know that there is a limit to how much effort people will put in, because it's not that hard to pirate literally anything, but plenty of people don't bother with piracy because it's a hassle.

It'll be interesting to see how things ultimately shake out. Google is in a bit of a privileged position though, given that they own the service and the browser most people are viewing YouTube. There's also more and more of a shift towards watching it on mobile devices and TVs, where they can control the client environment a lot more tightly. And at the end of the day, it is a solvable problem; beyond that, they don't have to even win the cat and mouse game. They just have to make playing it annoying enough that most people won't bother.