I dont think nxt being booked as the third brand hurts it at all. In fact I think thats why its so popular. Raw and smack down focus primarily on the sports entertainment and storylines, a lot of horrible storylines that either make no sense, or the fans end up not even caring about. Nxt on the other hand focuses on letting their roster showcase more of what they can really do, and HHH to his credit had let the fans decide who succeeds because of it. Nxts pay previews out did Raw and smack downs the entire year of 2017 and it wasnt even close. A lot of times their opening match would be better then raw and smack downs main event. They never miss a step either.
I don't see NXT as a third brand, and here is why.
NXT should have matches on the main WWE cards to be considered on the same level.
For example, Wrestlemania should have a NXT World Title match, an NXT Tag-Team Title match and an NXT Women's Title match. By having all three brands on the biggest shows, it makes NXT look equal to RAW and SD!
I would like to see RR have 10 RAW, 10 SD and 10 NXT stars in the Rumble (both men's and women's) and the main NXT Titles being defended on the big four shows. Also, I would like to see an NXT "Money-In-The-Bank" Match.
All of these things will elevate the NXT talent, and expose them to a wider audience, some of who don't get NXT where they live. I would have liked to have seen Bobby Roode, Shinsuke and others at WM or Summerslam while they were still in NXT. Let's see them on the big stage, and see how they handle themselves. Why not take the risk and throw some of them out there onto the big stage.
I remember one time John Cena telling Stephanie that Seth Rollins had to defend both his U.S. and WWE Titles at "Night Of Champions" before ALL titles are meant to be on the line (I know that it didn't happen this year either, because of the ridiculous brand extension). But I remember thinking "Okay then, so how come the NXT Titles aren't defended at "Night Of Champions" (which is what it was called back then), if every title in WWE is on the line?"