Just finished up with the game after a few hours, here are my impressions.
First of all, the gameplay speed has drastically changed, and while I do agree it was too fast before, I think they may have gone too far in the opposite direction. The action feels really sluggish at times. This also has the effect of the reversal windows being different than in the past, so it takes a while to get used to. I love the stamina system though. It causes the pace of the game to change as the matches go on. As for the chain wrestling system, I actually like it a lot. Adds an interesting layer of strategy at the beginning of a match and isn't around long enough to get bothersome, and if I ever do get tired of it I could always turn it off.
I was expecting the creation suite to be cut down, but it is really cut down. The options in CAW are much more limited than I expected, and I wasn't able to create the very basic CAW I create every year. I like the new UI for Create an Entrance, but it is also missing options. Though I really appreciate how similar to the actual models the CAWs are. They no longer stick out like a sore thumb.
MyCareer is obviously an idea that needs to be built upon in the future. It is a great basic idea, but the current state of it isn't as good as it could be. I played about an hour of it, and while I am enjoying it, it is very basic. Definitely not to the level of NBA 2K's Career experience Nonetheless, I am enjoying the mode.
In a more general sense, the models looking as good as they do makes the older animations look even worse than they have in the past. I like the new animations and I think 2K will add more of them going forward, but that should definitely be a huge priority for next year. The animations need to catch up with the models. It's a jarring difference in quality of the two.
I haven't touched Showcase or Universe yet, but I will say this. Even with all the issues I have with the game, I am having a good bit of fun with it. It's an enjoyable experience even while I acknowledge its flaws. I think the game is a good start for 2K and a good base to build upon going forward.