My hypothesis is that we are alone and the creation of sapient life is a very very rare thing.
The chance of life appearing, on top of the chance of the life being capable of getting more complex (multi-cellular), on top of the chance of life getting sapient, without counting the chances of the uncountable iterations between these steps...
There are too many stars, too many galaxies, too many galaxy clusters, and we've been here too short a time for me to believe that we're the only life in the universe.
Even on this one planet there are more ways to be alive than one can imagine, and those ways, once embodied, are very, very persistent.
Even forgoing the other comments on the number of universes/galaxies/stars/planets in existence, how do you reach this hypothesis given that you have only one example of evolution to draw inferences from. The entire train of thought is derailed that the only reliable information we have on evolutionary systems is our own system and, using this information, we can only conclude that every planet on which we have found microbial life we have also found sapient life.
Divide the known history of the Earth into ten million year increments, and the fraction of them with life is quite high compared to the fraction with intelligence.
The chance of life appearing, on top of the chance of the life being capable of getting more complex (multi-cellular), on top of the chance of life getting sapient, without counting the chances of the uncountable iterations between these steps...
...we can always uplift other Earth's animals.