I don't buy it though -- we're in an average planet on an average star, nothing about our environment seems to be particularly rare.

There are a number of Earth's attributes that we don't understand and have poor extra-solar data on. Particularly, the following:

Technically active plates after 4.5 Byrs. Effective magnetic core after 4.5 Byrs. Large amounts of surface water, presumably from our late heavy bombardment. Small enough to leave with a chemical rocket while meeting the above.

Also, at our current tech level, planets are very hard to even observe for existence, let alone their geographical features.

We simply don’t have data to support that claim, and the parameters required to make earth habitable for life (as we know it) are vastly more numerous than most people acknowledge.