I mean, I had a vita and the gyroscope control was more accurate than the stick for shooters but that's because I'll naturally adjust if it overshoots (if I go to above I'll immediately push slightly down in a feedback loop - so here what really matters is the precision, not accuracy and in fact I can even adjust the sensitivity to my preference). That feedback loop with the user doesn't work well in VR, if my hand overshoots I don't have means of resetting the position (I can only compensate, but it's extremely uncomfortable when you feel your hand in position x, look at it and it's at position y and that x-y mapping will keep changing over time - and of course it's even worse with your head PoV not matching your head movements). Of course there are lots of issues as well, how do you get the perfect initial position? After all gyroscope/accelerometers only measure movement, it can't know where it starts (for example for jogging you need a gps to get a measurement of position, just like you need a camera/laser sensor for current VR). For gyroscope in traditional gaming you usually use the stick to adjust a solid start position, which is not possible in VR as well unless you force the user to stay in a perfect pose at the start of every level after inputting arms length and height as an example, which would definitely be annoying quickly if you need to reset frequently).
And finally, you example (splatoon 2) only needs to compute 2 degrees of freedom in movement (rotation left-right - or yawing, rotation down-up - or pitching, since rolling isn't relevant with a dot target), while VR systems depend on 6 degrees of freedom (yawing, pitching, rolling, elevating, strafing and surging - all of these for at least 3 devices at the same time: your head, left hand and right hand). Unfortunately controls in VR are quite complicated, and accelerometers, gyroscopes (and magnetometers which are also used in VR systems to know the reference to the floor) are simply insufficient (but necessary since the positional sensors can't keep track all time with occasional occlusion, such as having one hand passing over the other or leaving the tracking area), which is why the same sensors on the switch are used in every VR headset and controls in addition with even more sensors and algorithms.
EDIT: the camera system also helps a lot with defining gaming boundaries in the room and being able to quickly see if I accidentally leave it, I already punched my monitor once and that's with a barrier that always get visible when I approach something in my room.