Earth is a graveyard of species. Looking at the geological record, more than 99% of species that ever existed here have gone extinct [1]. Overwhelming majority of them long before we showed up. And in any case, this planet will not support life forever [2].

Believing we have no destiny outside Earth is believing we have no destiny at all.

[1] https://en.wikipedia.org/wiki/Extinction [2] https://en.wikipedia.org/wiki/Future_of_Earth