I disagree, if the central theme of brotherhood was the game, it was still poorly done. The fact that you had to watch a mediocre anime for any semblance of a back story on these characters is already a major fault. If this was incorporated INTO the game we'd have a good starting point. And it was sorely needed as the current story is light as hell.
I constantly felt like I was forced to like these guys. But was given very little to actually care.
There are events in the main game that COULD lead to building a stronger bond with your brothers but are done so in such a terrible way that cheapened the entire premise.
Gladio going off somewhere for no explanation. Ignis going blind off screen in an event that made zero sense to break up the group. Prompto suddenly being a clone/mt stage one whatever and brushed aside.
If the world of Ruin had me re-recruiting these brothers like in FFVI, helping them solve their current issues that would be amazing. Instead of we get a terrible reunion at a convenient railroaded section of the world.
Hell if some events from the anime concluded in the game, like Ignis's search for his recreated recipe, it would be good.
Even the last fight of the game, your bro's are knocked unconcious for whatever reason, oh never mind it was so they could do another cheap ass DBZ fight.
They couldn't even commit to having Noct say "I love you guys."