Yes, I understand the argument - but it doesn't alter the fact that those excuses can always be used, and probably always have been. Quantum mechanics was more

Yes, I understand the argument - but it doesn't alter the fact that those excuses can always be used, and probably always have been. Quantum mechanics was more revolutionary than general relativity, but came almost immediately after and was simpler (after the conceptual leap) to study, which rather undermines the low-hanging fruit excuse.