I don't think the problem is so much more prevalent in olympic weightlifting than in any other sport (including cycling, soccer and many others). I know of certain cases of doping, it's worse in some places than others, but here's a story for you.
One lifter I train with snatched 170, clean & jerked 210 as a 94kg lifter, so that's pretty elite standard. It's years and years after, his body is screwed (bad wrists among many many other problems), he isn't anywhere near as focused and is old by oly lifting terms. Training twice a week (if that) he still powersnatches 130kg for reps, clean & jerks 165kg easy, it's incredibly unlikely that a retired, rarely training lifter would bother to be on anything. The point of all this is that you can still lift damn good weights, world standard, while being clean.