Also no Ash is the canon protagonist of PSO2. You even see him in the pictures of the Story Missions. We just play his story with our PCs thats all.
So I'm going to stop you there. Ash in PSO2 serves the same role as Derplander from FFXIV - he's the poster boy for Sega to use when it's not feasible to use the Guardian (for obvious reasons) in promotional artwork, screen grabs, etc.
Ash literally does not exist in PSO2. He is a stand in, and nothing more, for the Guardian. He's the protagonist of the anime, yes, but the anime also isn't "canon" in the sense that it's the defacto version of PSO2's storyline. Ash and Ethan are not comparable.
Everything else you posted completely skirts around what I actually stated - Ethan Waber is the canonical protagonist of Episode 1, with an established personality, family, and friends that all are part of his story. The PC in PSU is introduced in Episode 2 as the apprentice of Leia, another Guardian, and their story is then bound as well to that of Ethan's, who remains the central protagonist throughout PSU. Without Ethan, the entire plot and focus of Episode 2 basically falls apart, as Ethan's "defection" to the Illuminus as a double agent is essential to both motivation Leia and the PC to chase after him, his sister and Karen to try and find out why he "Defected", and more importantly, to actually reveal the motivations of the organization, the origins of Magashi, and reveal to the player who the one orchestrating everything behind the scenes is.
Without Ethan, literally none of the events of PSU's second or even third episodes would work. You cannot replace him with a generic, emotionless PC. It'd be like trying to take Final Fantasy VII, and remove Cloud from the equation and replace him with a generic PC. It does not work.