Re: Why the Xindi never appear in TOS / TNG / DS9 / VOY
Andorians were never seen TNG, neither were Orions iirc so it's not much of a stretch to say they were there just never seen.
I think we saw an Andorian twice in TNG
"The Offspring" Hologram only
On the continent of wild endeavour in the mountains of solace and solitude there stood the citadel of the time lords, the oldest and most mighty race in the universe looking down on the galaxies below sworn never to interfere only to watch.