Something that I don't so much believe as assign a higher probability than other people.

There is a limit to how much technology humans can have, how much of the universe we can understand and how complicated of devices we can make. This isn't necessarily a universal IQ limit but more of an asymptotic limit that our evolved brains can't surpass. And this limit is lower, perhaps substantially so, than what we would need to do a lot of the cool stuff like achieve the singularity and start colonizing the universe.

I think it's even possible that some sort of asymptotic limit is common to all evolved life, this may well be a solution to the fermi paradox, not that they aren't out there, but no one is smart enough to actually leave their rock.