I have a theory now this is a little out there so bear with me and I may of been a little baked when I though of this: But the reason why we exist is we are avatars of other people, and not just that every animal on the planet is just laughing at us, with the exception of ourselves, so for example you are not the pinnacle of evolution, you are the lowest point, hence just backwards; and there are perhaps species watching us and laughing at our mediocrity factory: out there in space. However in the long run it works for them, because we show them exactly what it is to go wrong. We exist simply because, we have to to show any really sentient race all the mistakes they could make. We can't meet intelligent life out in space because we are their experiment. https://www.youtube.com/watch?v=JWVshkVF0SYp/ Because there's bugger all down here on Earth.
It's not so much you've been replaced more that somewhere out there, someone is using you as an experiment, to work out just how fucked up they could be if they were human. Any sentient race just looks at us a s a sort of Bog Brother, just like Big Brother on TV, they laugh and point. Welcome to your reality, you are never going to get that much better because you are the butt of some cosmic joke.
"The best proof that there are other intelligent creatures in space, is that they don't contact with us"
Indeed and to quote a wise Sage for the second time "Let's hope there is intelligent life somewhere out in space 'cause there's bugger all down here on Earth."