I played a ton of ARMS at Dreamland, and my impression is that the game is a bad, hard-to-control version of Virtual On.
The motion control problems stand out a ton when the game gives you punches with both arms instead of throw, the former of which is massively unsafe and generally not something you'd do to a target you intended to do the latter to.
I tried out the entire cast and Ninjara was mad good with Mummy being terrible. Ninjara's evasion, dash length/speed, teleports, stun arms, chakram arms, and high-damage throw (because his is a combo) all contribute to making him stupid good. Ribbon Girl is probably second best, but she doesn't have a boomerang-style weapon that hits from behind like Ninja does.
I can totally see how they'd screw over people not using motion controls as well, since stretching weapons at range and piloting the individual boomerang arms require motion use.