The receding ship disappears over your horizon, hull first. Is this proof of the World's rotundity? No. Why not? Because the ship can be restored to view with a telescope at the same altitude as your eye was at.
If it was so, you would be right. But this is not the case.
As I said a couple of times already, there is no restoration and, moreover, there is
no need for restoration. Forget eyesight. It might have been interesting in the era of that Parallax guy but not any more. Everybody for a small amount of cash can have a binocular or a camera that is perfectly capable of demonstrating this phenomenon. Don't compare eyesight and zoom, there is need for that, I repeat (if you do, you decide
nothing about the shape of the Earth, just about your own eyesight; that might be interesting for your ophthalmologist but not for our discussion). Check the movement of a ship inside the distance zone interesting for us with zoom, from start to end, and you'll see it sink. You'll see it sink in a distance when you're still completely able to see every single detail with your fixed zoom and there is no need to zoom any closer.