> For all we know the Universe may be teeming with intelligent life and we just don’t recognize it as such.

This is my preferred answer to the Fermi question as well. Unless two civilisations are in a precise (and likely small) window where they both can and want to communicate, it's likely the less advanced one wouldn't even recognise the other one. Especially if the other one doesn't "want" to be recognised.

Yup, and just look at how difficult it is for us to recognize different kinds of intelligence on our own planet too. We've just started figuring out that animals like crows have complex cognition.