This ignores a lot of nuance. There are a large number of species which have independently evolved significant intelligence, many of whom have been observed to

This ignores a lot of nuance. There are a large number of species which have independently evolved significant intelligence, many of whom have been observed to use tools at a level comparable to our geologically recent ancestors. We currently occupy the "use tools to dominate the world" niche - any other species that adapts to use more advanced tools will come into direct competition with us. Regardless of how easy or hard it is to get into this niche, it's unlikely that more than one species will occupy it at any given time. However if we were to suddenly disappear, there are many candidates that could potentially get to our level within a few million years. There is no reason to believe life bearing planets are rare (all evidence points to earth-like planets being common), no reason to believe the evolution of sentience is rare (depending on your definition of sentience, it happened more than once here), and no reason to believe it's rare for sentient life to produce civilization (for humans, civilization has emerged independently many times).