a totalitarian society

Afaik Russia isn't totalitarian yet. They're "only" authoritarian. In the latter there's still a lot of private life left that isn't dictated by the state and therefore a lot of room to wiggle in a survey. That obviously doesn't mean you can get surveys with a western standard, but you can indeed gauge public opinion. Real authoritarian regimes are actually quite rare. I can't think of any examples besides North Korea and Afghanistan that clearly fit at the moment.