By graffiti, I assume you mean tags, i.e. not the ones with some artistic value?

I live in Zurich and also wasn't under the impression that it's noticeably worse than elsewhere, but it's certainly an unnecessary eyesore.

There was some reporting on it recently, saying that a major issue are private building owners. Public spots are usually cleaned up quickly. They said the city has some form of very cheap service/insurance offering that building owners can get, which assures that any reported sprayings will be washed off by city workers within x days, but that this service seems to be not widely known. So at least, people seem to be aware of the issue and doing something.

Nothing preventing tackling both issues at the same time, in any case.