I mean it wasn't great and I'd always turn it off until I got the new 3DS with the eye tracking.. Now it's perfect and I very rarely turn it off.

Yes, because almost no one had a glasses-free screens available at the time. But we have VR already,and low pixel count is a huge problem with it - 720p screen is going to be horrendous no matter what you do, it's been tested before and it's just not pretty.

Have you used a 720p VR headset? I have. I spent 400$ on one. It's unusable. It's out of the question. At 4x that resolution everything is a blurry, blocky, unreadable mess. 720p isn't even worth considering.