The Romulans, also, were called upon with lesser regularity to bring spice into the lives of our STAR TREKian heroes. But I was always more interested in the new species TNG put in the pot and, fortunately, the pot got stirred, a lot. The Bajorans are a TNG invention and where would this franchise be without the Borg? Or Ferengi like Quark? All of these and more are very good additions to the lexicon of STAR TREK. So, maybe I misspoke myself when I said TNG didn't rely much on TOS, but it brought so much more to the table that was their own. And I still maintain that Discovery should, as well. But ... we're looking at Spock and Pike appearing in Season 2. We've already seen Harry Mudd in action and STD is even drawing on obscure aliens found in TMP. That should be enough TOS callbacks for anyone. Let's see Discovery put a little effort in and veer away from nostalgia, for a long while.