It's not that the Mythos is so often "dumbed down" to be made fun of should be worrisome. It's that the very idea that our modern society can make fun of the idea of an uncaring, nihilistic universe and doesn't have to dumb any part of it down that should be worrisome.
It means we're closer in mindset to the horrible things that lurk in the Mythos than we realize.
Think about this: what do you do as part of your daily life that would be considered impossible, madness-inducing, or cult behavior to someone from the 20s, who'd never heard of a supersonic jet, driven faster than 10 miles an hour, or couldn't even conceive of the notion of m-theory without being driven to fits of disbelief? How many video games, starting with the ever so innocuous A Link to the Past, have taught you to think in four or more dimensions? The very notion of the internet or a flash mob is frightening to contemplate under these circumstances.
Things to think about.