Comment by wk_end
The thing is, the 3DS was a success mostly despite the 3D, rather than because of it. No one was excited about it or all that impressed - remember that initially the 3DS was such a flop at launch that Nintendo needed to pull a Hail Mary, cutting the price and launching the Ambassador Program. Or consider how successful the 2DS was.
The 3D on it is a very neat trick, but it's mostly a distraction and there's something "uncanny valley"-like and unpleasant about it. I almost always play with the 3D slider off; it's easy for me to see why Nintendo gave up on it.
The second revision with the better “head tracking” screen (I don’t remember how it worked) was much better than the launch model.
But mostly, you’d just turn 3D off. It was a gimmick, cut the resolution in half, and doubled processing requirements.
It just worked way better as a 2D screen. As you said, 2DS was good.
They should have just made the DS2, not gone for 3D. But such was the time.