Huh? We have flying cars. They are called planes, and they take a lot of maintenance to keep from falling out of the sky.
But let's change the question up a bit... There are billions and billions of flying intelligences on this planet. Birds, insects, even mammals. Nature has already created that. We've created things that are even better at flying fast and carrying more weight. So simply looking at 'flying cars' and saying they didn't happen so AI can't happen is at the least, very ignorant.
If nature can create something randomly, we can create something directed in a shorter period of time (well, we don't really have another 4 billion years to try). AGI is an eventuality.
GI already exists, AGI is only speculative if you believe that humans go extinct before they get complex. We can perform scientific experiments on GI at this time.
An alien invasion is speculative at this point because there is no alien species on to which we can base any scientific refutation. It is not impossible, it is simply impossible to define any probably of occurrence.
But let's change the question up a bit... There are billions and billions of flying intelligences on this planet. Birds, insects, even mammals. Nature has already created that. We've created things that are even better at flying fast and carrying more weight. So simply looking at 'flying cars' and saying they didn't happen so AI can't happen is at the least, very ignorant.
If nature can create something randomly, we can create something directed in a shorter period of time (well, we don't really have another 4 billion years to try). AGI is an eventuality.