The Fermi paradox is unlikely to be answered by something making it very unlikely for our chimp level ancestors jumping to human level. The number of Homo species on the planet that co-evolved to human level intelligence suggests this is not extremely difficult.

What is a huge filter is the requirement of a stable climate over million of years. The key to this is the Moon which keeps the Earth's axis of rotation from wandering over a wide angle on geological timescales. The Moon is so large and unlikely (we still don't have a good theory for how it was formed and captured by the Earth) that this alone could explain the lack of other intelligent life in the visible universe.