I'm all for bitching about hitbox problems like hits registering when you're clearly shooting outside the borders of the character like it's the case with Pathfinder. But I feel like bitching about the size of hitboxes makes no sense, since in life there are people of different sizes and men are generally larger than women, so different sized hitboxes makes sense. I think Respawn did a good job balancing the legends. Gibraltar has a big hit box sure, but he's got a shield that hides his entire body while ADS, leaving only his legs and head exposed and he can reduce it even more if he crouches. Gibraltar also has BY FAR the most powerful offensive Ultimate in the game. I have killed entire teams with it. Unlike Bangalore's bombardment, you have almost no warning and you can't really dodge the blasts easily like you can with hers, you just have to try to get to shelter or out of the AoE before you die.
As for Caustic I do think the AoE for his ultimate is way too small, but if they made it much bigger then for me that would balance out his large hitbox.
In a game like Fortnite where no character you play as has any different abilities than any other, then yes, there it makes sense to have same sized hitboxes so nobody has an advantage but when it comes to Apex I feel like some characters' ultimates are OP and they should have that large hitbox to balance things out.