Considering the size of the universe, I don't give that much credit to the Great Filter solution on it's own. Same goes for Dark Forest because I believe it greatly understates the potential of advanced technology.

The Rare Earth solution is my favourite. Assuming the Fermi Paradox is accurate - we're not alone and noone's interfering with us, but we can't find anyone - maybe complex life could just require MANY more specific conditions and our little planet meets them all. There really might not be any aliens if we combine this with the Great Filter.