the question is about what does fundamentally exist, not what you perceive through eyes or experiments.
do particles exist or not? is it all just in your imagination because you are a "brain in a vat?" what about the everettian multi-verse, is that real or not?
by saying these SCIENTIFIC questions are trivial to answer because you can hold a GPS receiver in your hand is to completly misunderstand what is being discussed here
nobody said something else deliverd on this question. but neither did science. it's the consensus in physics right now that it can't say what "really exists", this is not a fringe position