It's true that contemporary (23rd century) Earth is never seen in TOS. Of course, the idea for a Trek through the stars. Boldly going to where they have never been before. New life and new civilizations.
If anything, getting away from that makes it less like Star Trek. Andorians, Vulcans, etc. were new to audiences then. We should see new species, and new civilizations, not a concentration mostly on the ones already well known.