Earth is the home of Starfleet Command and the Federation Council. There's no way that Earth could not
be an important part of the story.
TOS episodes were conceived as, if not written as, a metaphor for the human condition. Regardless of storylines and characters, to change that now would be to abandon entirely GR's vision.
I can't spend a lot of time writing responses to these threads but I've seen a bunch of "fans" over my 40 year history with Trek that don't seem to get it.