It's fun. And that's the most important thing to start with.
If the goal is to get through a career in a week or so and have a good fighter at the end of it to play your friends with, then it's not bad. Training will rapidly improve your fighter's base stats, but there are drawbacks if you're too aggressive - for instance I have had some fights where I trained nothing but leg kicks, and my leg kicks were -15 for the next fight. Rogan/Goldberg even mentioned that there were "rumors" that I had a leg injury going into the fight which I thought was pretty cool.
If the goal is to immerse yourself in an alternate UFC universe, create rivalries with other fighters, view other PPV cards, etc, then it's terrible. The only thing they did better in this regard in comparison to last time is make Bruce Buffer actually sound legitimately excited before your title fights - they even dim the lights after he does the "ITS TIME!" like in the real UFC. He still doesn't "sell" your name the way he should, but it's definitely WAY better than the last game.
My opinion falls somewhere in the middle. It feels more like a "mobile" version of a career mode than a legitimate console sports game career mode. It's simplicity will either be a drawback or a benefit depending on your style. It is obviously clear that the devs were instructed to focus on other game modes and to make just enough improvements in career mode for them to market the game.