Yup.<quoted text>We *know* that GR doesn't take into account quantum effects. The problem is finding a theory of gravity that *does*.
If anyone finds a case where all or part of a scientific theory is false, then that theory is either changed or thrown out.
And it is well known that GR will have to be modified in some way since it isn't a quantum theory of gravity. The problem is two-fold: 1) we don't have any current evidence specifically relating to quantum aspects of gravity, and 2) merging QM and GR has proven to be quite challenging. We have a couple of possibilities: string theory and loop quantum gravity. But because of the lack of evidence, we cannot test between these.
Second, in practice we still use Newton's theory of gravity in many cases: it is easier to use and gives very good approximations in most situations. So even if a quantum version of gravity is found and verified, GR will still be used for those situations where quantum effects are small and relativistic effects are significant.
But the expansion of the universe is NOT a quantum effect. The basic of the BB theory are not due to quantum effects. So GR works quite well until you get up to energies that are far, far higher than anything inside of stars today. The basic theory is still going to be valid even under a quantum theory of gravity.
And String Theory fails too.
"If anyone finds a case where all or part of a scientific theory is false"
My new Theory "the Theory of Quantum Relativity Strings"