That observation is also consistent with the top of a giant starfish or doughnut or snow man -- any shape of sufficient size. Should we assume the earth is any of these shapes?
No, but if observations do not conflict with the earth being any of those shapes, then you should not dismiss them out of hand.
What is the difference between not dismissing any given model, and not accepting any given model?
It's the difference between disproving a given model and choosing to not even consider a given model. If you cannot show a reason why a particular model is not true, then there is no reason to assume that the model is false.
It's sort of like the difference between you winning and me losing. Just because I lose, that does not always mean that you win. Or, to put it another way, just because you find problems with RET, that does not mean that FET is correct.