#4 NXT stars failing on the main roster
Some stars who really didn't do much of note in NXT like Baron Corbin, Braun Strowman and Elias, have had much more success on the main roster than stars like Bobby Roode and Finn Balor.
While that may be a harsh reality for some to accept, there have been dozens of cases of NXT standouts failing to reach that same level on the main roster, including but not limited to the likes of former studs such as Sami Zayn, Bayley, and Tye Dillinger. The jury is still out on some stars, including Shinsuke Nakamura.
The bottom line is that the audiences for NXT and WWE are more different than you might think. Therefore, when watching the current NXT product, it's not pessimistic if you think to yourself, "the main roster is going to ruin some of these stars whenever they get called up".
That's reality. Unfortunate - yes, but reality, nonetheless.