You have a RE mindset. That's why your eyes can't see objects flat. The computer screen is flat. If you force yourself to think it like a sphere, then you will inevitably have eye problems because of eye-brain mismatch.
That's not my point. The problem is that without glasses, my vision is a blurry mess (near and far, astigmatism.) So, any flat object has a hazy outline that kind of looks like it could be round or flat. I can feel the computer screen, but I can't feel the horizon.
With glasses on, the world distorts. And trust me, it can distort pretty heavily. 16:9 is approaching 4:3 for me, and objects get shifted toward the center of my vision. I can't trust that vision either, because round objects get distorted as they're pulled towards the center to look flat, and vice versa.
My mindset isn't RE. I do believe in RE, but I could absolutely be swayed. Just not by my own perceptions. Which is a problem, because the whole idea is to trust only my own research and my own perception. I love hiking. I've climbed up a bunch of mountains in my area, and the horizon looks rounded with my glasses on from the top. I can't really make it out without them.