Really? I mean, I recall Gladius advancing his relationship with Noctis as the story progresses, due to a rising tension between them, so much so that they have a falling out and he leaves for a while. Prompto has some personal hangups about feeling inadequate, and you can talk to him and help bolster his confidence. Ignis....well frankly I think he does stay fairly static as I recall, he's just "Poised British Posh" from start to finish, though he does become more pensive after that significant event happens to him offscreen later in the game.It establishes that they already are friends, sure, it doesn't develop the characters or show their friendship be formed and advance.
My biggest issue with FF15, wasn't the interaction of the guys, I thought that was frankly just fine. My issue was the disconnect in how Noctis would act when you have control of him, versus in the scripted scenes. It was pretty apparent from his tone and dialogue, that Noctis, when running around, doing quests for his subjects, and just meeting and interacting with them, that he's actually a pretty chill, laid back guy. He never comes off as annoyed when being asked yet again to help someone, he seems more than happy to do something to help improve their lives. He makes jokes with his friends, the people, is willing to pose for silly pictures, do goofy touristy stuff, and overall, just act like a well adjusted person.
...and then a cutscene kicks in, and he's acting all emo and edgy, and angry and lashing out at people.....and then it's back to me controlling him...and he's all chill and laidback dude.
THAT annoyed me to no end, because it felt like the game and cinematic story had 2 different protagonists. One I genuinely enjoyed playing as, the other an annoying JRPG/Anime edgelord that I wanted to slap.