Bit worried it'll split up the user base and skill levels, similar to k/m use on consoles, so I'm not really sure. Think for consistencies sake I'd probably just prefer most games stick to dual sticks. It's not exactly a bad thing if in competitive games everyone is on a level playing field. Or at least as many people as possible.
Considering that every standard controller for the system has it built in, I don't see how it would split up the user base.
What it would do is raise the skill ceiling for the game, and that's something the matchmaking system should take care of anyway.
Many console gamers seem absolutely terrified of raising the skill ceiling for some reason though, as if skill-based matchmaking wasn't already being used by games.
They should put it via firmware update for every game available and why not, also to handle the major UI stuff.
Unfortunately having the Gyro emulate the right analog stick input in games doesn't work that well for most of them due to acceleration, limited sensitivity, 'sticky' aiming, and other aim assists that games have built in to try and make analog sticks feel better to use.
It may still be better than nothing at all in some games though.
I never singled out Splatoon I'm just speaking as a new Switch owner and so far Breath of the Wild has force me to fab about with Gyro controls in a few shrines (despite me not wanting to) and in Mario Odyssey they made it unnecessaryly harder to do that spinning move with Cappy if I don't use the Gyro/Motion control.
Motion controls; i.e. 'waggle' are bad. Those shrines in
Breath of the Wild, and requiring you to shake the controller in
Mario Odyssey instead of pressing a button for certain actions was terrible.
Gyro aiming is great (and optional).
My preference is for Gyro aiming to activate when aiming down the sights - though some people like to have it active all the time.
Splatoon's restriction on aiming with the analog stick, forcing you to use the gyro for vertical aiming is not something that I like.
I actually thought that
Zelda's implementation of gyro aiming on the Wii U and Switch was fairly poor, as its sensitivity is linked to the analog stick sensitivity, it seemed to have a fairly large deadzone, and it lacks the haptic feedback that you get with the Steam Controller.