@flitcraft It really doesn't, though. Gnosis caps Arcana, but it's the only Power stat that does so for powers. A Primal Urge 1 Werewolf or Blood Purity 1 Vampire can still buy every level of Gift/Discipline they want; though the Power Stats do serve as requisites for some of the higher end merits. Conversely, both the max level of Arcana and the number of different Arcana you can have are limited by Gnosis on the low end.
On top of that, it also governs the pool you have to draw from and the maximum amount of pips you can draw per round - which has become fairly standardized in 2e. On that it's a level playing field.
Where it most counts is in terms of skills and stats; having a power stat higher than 5 means you can buy stats and skills at higher than 5, and allowing that for one group while categorically denying it to another is unfair. The argument that 'mages can boost their stats' doesn't hold anymore either, since
A> Physical disciplines now passively increase Strength or Stamina by their rating (And Dex, if you go for that obscure bloodline that has it) - that's without having to spend or activate anything.
B> Werewolves have gifts that also increase stats, on top of the stats that they get from shapeshifting.
Further, Gnosis still limits the amount of spells a mage can have active at any given time. The symmetry would be limiting a vampire to only a certain number of Disciplines active <both passively and used directly against someone> or the number of Gifts they can have up at any given time - neither of which is a rule that exists. If anything, Mages depend on their Gnosis far more than the other supers depend on their respective power stats, so if you hobble it while not doing the same for the rest you might as well just not have Mage there to begin with.
tl;dr Edit - Mages start off not being able to do a lot of things that other supers can do right off the bat; Gnosis helps them overcome that restriction before it starts giving them any real bonuses.