Please describe the experiment that tests general relativity in a lab. We can test quantum mechanics in a lab and prove things that conflict with general relativity.
GR is not needed at all for GPS to work correctly, nor is it needed to explain any of the other alleged proofs of its correctness. Meanwhile, it can’t explain things like galaxy rotation curves at all and ends up demanding complete absurdities that require physical impossibilities (cosmic inflation, black holes, neutron stars, dark matter and energy and so on).
That GR now requires the addition of 33 times the amount of observable stuff in the form of “dark” matter and energy in order to hold it together demonstrates that it is a dramatically failed theory and not a successful one at all; and as such, a reasonable person is all but required to question whether this theory has outlived its usefulness. There are more things GR gets wrong than it gets right - I could list phenomena that don’t fit the GR model, yet appear to exist, or alternatively those that are demanded by the model and don’t appear to exist, all day.
It’s well past time for a new theory more appropriate to a post-discovery-of-electricity era.
I’m only claiming the veracity of GR as to its primary purpose: to explain how gravitation works; via the curvature of Spacetime. Evidence can be seen in Mercury’s precession (this month is the centennial of Eddington’s experiment), gravitational lensing etc. If GPS did not take GR into account it would be about 7 miles off.