And ENT didn't bring in a bunch of TNG races. The main players throughout the show were the Vulcans, the Andorians and the Klingons ...
Also seen were the Romulans, Ferengi, Orions, Tellerites.
Thing is the writers showed they were capable of creating new interesting species, so why the "retreads?"
And with the exception of the Ferengi (also just one episode), none of these were species from TNG. And two of them were only ever seen in TOS until that point as well! So I don't see how the "TNG retreads" argument is particularly valid.