Supposedly he has an open invitation to join NXT whenever he wants. I think he's happier being a big fish in a somewhat smaller pond than becoming another cog in the WWE machine (don't mean this in a bad way either).
I concur. WWE has so many good talents, atm, but I feel like when it comes to showcasing them, I feel that WWE is really not putting their best foot forward when it comes to the booking and rather keep flaunting the days of yesteryear and Cena and whatever over truly moving forward with their big roster.
Kenny Omega and what he has done at the G1 Climax and the Tokyo Dome show, he has shown that he can be a big player and draw for NJPW which is quite surprising given his start. He started during the Canadian independent scene (there's a video of him fighting for this Champion of Anywhere match and I really think TNA's The Final Deletion was inspired off of that), wrestled in DDT which is full of weird stuff including wrestling sex dolls, teaming up with Kota Ibushi where they were known as "Golden Lovers", to wrestling that nine-year old girl, to eventually wrestling Kota Ibushi in a long main event in Budokan Hall in front of about 11,000 people to eventually finding his way to NJPW and slowly building himself to be a superstar there.
So yeah, I don't blame him if he wants to stick around in NJPW for a while. He can do a lot now there than if he is in WWE/NXT where he could just be another guy in the WWE machine. It's not every day you'll see him going 46 minutes against the present/future of NJPW in front of 26,000 people. I do think he'll win their big championship eventually. He seems to have plenty of ideas lined up regarding NJPW and them growing, so it's definitely for the better if he sticks around. I don't watch WWE anymore, but love watching NJPW, so I don't mind this at all.
Just because WWE signed Shinsuke Nakamura and AJ Styles, doesn't mean I'm going to watch their product again. It just means that I'm not going to watch Nakamura and Styles as much as I want to.