It's less than you might think proportionally. Only 10-15% use VPNs regularly and only a
third have ever done it, and it's pretty much always just for banned entertainment. Even though the political posters are loud there aren't really that many of them. It doesn't help that the Chinese on the normal net speaking English are disproportionately political, whether because they're more affluent and educated or just because they're from HK.
I've worked with highly-educated, English-proficient, Chinese. Only two have ever been (privately) critical of the regime and even they weren't using VPNs for more than movies, and I'm not sure both were using VPNs. Even the more political one bought into the "China can't be a democracy yet" party line, though he supports HK. The other ones are all apolitical and unquestioning. Even though "Marxist theory" is a required class for all university students they couldn't repeat anything from it; one didn't know what the Cold War was even though that figures heavily into Maoist theory. YouTube was amazing to them though and they were spending hours on it.