If you feel nothing going from Splatoon matches back to walking around Inkopolis, then alright. Better comparison, if you felt nothing going from Super Smash Bros. Melee to a lot of other games in its time, then frame rate isn't a sensitive point for you.
Personally, beyond the look of it, a higher frame rate typically carries with it a vastly quicker response time between controller and on-screen action. I feel that the connection between player and character or on-screen action is more in sync with a higher frame rate. From my limited understanding of it, it technically has to feel and be more connected. For me, the difference between a higher frame rate is drastically more pronounced than a higher resolution.
I'm not the kind to say that 30fps is garbage; Breath of the Wild controls just beautifully as it is. It's just that at the 60fps of Splatoon 2, there is an extra touch to playing as an Inkling that gives me an extra heightened sense of the Inkling's world.
In short, it's about the (personal) feel!