To me NXT kind of has "main roster" and a "developmental roster". I will admit there is various levels of overlap though.
Guys like UA, Gargano, etc. These are the guy and girls that tour the country doing the nationwide shows. These are the people you see on TV every week that are probably closest ready to be moved up. This is kind of the "main roster" in NXT.
Then there are the NXT house shows that tour around FL and play small venues where seating may be 200-300. These are the guys you rarely see on TV. Usually they'll have one or two names from the nationwide tour on the card, but its mostly the guys they are trying to develop. I kind of think of this as the developmental part of NXT.
Yes I know but there was a time when you didn't have to be a 15 year indy vet to get on TV more than once every 6 months. There was a time when there were live mic promos so guys could actually get better on the stick, there was a time when you had to have a character beyond "indy legend who wants to be the best". Now NXT's only focus is on 5 star matches, they don't even try to make the stories make sense anymore. Why did Gargano as champion challenge Adam Cole to a rematch, even though he had already beat him clean in a 2/3 falls match? HHH went "I need a 5* match and there's nobody who has been built up to challenge Gargano so let's just do a rematch for no reason". That's why he booked Gargano/Ciampa at 57 straight Takeovers even though he completely lost the plot of the story halfway through, because all that matters is booking a match that smarks will jizz over.
I remember when people like Baron Corbin, Bo Dallas, Dana Brooke, Enzo and Cass, etc. were allowed on TO cards, because back then HHH knew that guys needed opportunities to improve; nowadays non indy vets are lucky if they can get a 5 minute match on a tv taping, let alone a fucking TO match, and the end result is HHH constantly having to sign new indy guys because he can't be added to build up anybody else.
I bet the next TO is going to be
Because who else could you even put on the card who wouldn't require effort to build up?