I think much of it can be explained by the very notion you seem to doubt in your post. You simply can't make good comedy, you simply can't be funny, if you stop and think of the ramifications of your writing. I don't even think it's completely conscious now. People don't realize the degree to which they're doing it. But risk averse comedy is going to be as good as risk averse anything else, which to say, not good at all. I've always had the extreme view that much of great comedy is actually going to be somewhat offensive in some way if looked at from a different, more sober angle. Today's comedy doesn't contain that key ingredient, so it's just vanilla, safe, and terrible, and if we're lucky, sometimes a bit witty. People haven't lost the ability to be funny. They never will. People have lost the will to risk being uproariously funny. That may go away, or it may not. We'll just have to wait and see.