Motivation wise, it's clearly a money grab. Is that a bad thing? Nah, fanservice may seem cheap, but it gets people in seats, and is still hype. Vegito was dope in the Goku Black arc, but the retcon was upsetting. Female SSJs were cool, then having one be a Broly-esk character was cool. Like, Super has been giving us fan service again and again, and I'm not upset, because it's at least somewhat interesting.
But therein lies the issues I can foresee. Is Broly's reboot going to be interesting? Just because they are bringing him back does not mean it's going to be good. They made two broly movies after the first, and they were garbage. So there is a real possibility that hes going to suck in this movie too. Animation wise, this is the best looking anime movie of the year, but the story is just as important. How are they going to explain away the fact he wasn't picked for the tournament of power? Are they going to reference the clear relationship between him and Kale? How is freeza involved with him? Is Beerus or Whis going to have knowledge on this person? There are a lot of ways that this movie can fall flat on it's face.
One thing I might like to see, is an attempt to make Broly a part of the show. In true DBS fashion, they may try and have anime episodes dedicated to this movie once the show comes back. If they do that, and the events of this movie become even more solidified in the universe, we could see a much more fleshed out character. Would he be a good guy after? A reoccurring villain? If he's strong enough to push Goku and Vegita, will he ever face off against Jiren? What kind of power scaling is there going to be? If he's a villain, how is it that he's this strong? These are all question I imagine will be answered within the scope of the film, but that wont stop me from asking them in the meantime.