We develop models of reality based on their predictive power and reliability. I understand where you're coming from with respect to quantum theory, but if you're saying that both sides are simultaneously right and wrong simply because we have a tenuous grasp of the quantum notion of "perspective," insofar that it means an infinite number of possibilities can coincide with each other simultaneously, I'm going to disagree with you.
With the sole exception of quantum theory, everything else we observe about the natural world tells us that we live in an objective, grounded reality.
Consider the following example:
If someone I've never met steps on a plane and flies across the globe to land in my state, visit my workplace, and stop by my desk while I'm on a bathroom break, I have no way of knowing that they even exist, never mind that they came to visit me. Sure, I can conceive of something like this happening, but that's different from knowing with any reasonable degree of accuracy WHEN and HOW this situation might take place, if ever.
If the imaginary visitor stops by my desk and leaves a Post-It note that reads, "The author of this note does not exist," leaving and going home before I get back from the bathroom, I'm going to have a hard time reconciling the content of that message with the obvious fact that, clearly, someone left a note.
It's an interesting thought, quantum theory and the way you're interpreting it, but you're talking about it as though it's as concrete and certain as the pastrami sandwich I had for lunch this afternoon. The fact is that it's still a blossoming field, relatively speaking (haha puns) and we don't actually understand as much about it as we do other disciplines.
Yes, our reality is concrete, this is a sphere, we can predict and measure what is there.
The reason it is concrete is the same reason why an electron instantly appears in the place immediately observed.
However, when not observed, it is probable, and even then, its behaviors are out of our understanding.
What we know, is that the further into the atomic level you go, the more wavelike something is, the more unpredictable, the more infinite it is.
However size is only relative, or not relative, depending on what your reality is.
The Universe is expanding, stretching space-time infinitely, spreading every galaxy, star, planet, atom, molecule, and particle, further and further apart.
You can literally be the size of an electron, or the size of a galaxy, but relative to you, you are the size of yourself, even though you could be stretched across what would be light years relative to someone else.
With this, it is forever, we are the size of anything, infinitely.
We are all possibility, relatively.
But only to us are we this way, and only to us is the Earth only one shape.
But change your relativity, and it becomes probable, and incomprehensible.