It's not an uncharitable reading if Gould stated his claim unequivocably.
Your alternative claim is just factually wrong. The population frequency of an allele under selection pressure can change within a few generations.
For example the HbS allele, that confers both sickle cell trait and malaria resistance, became less common among Africans transported as slaves to regions where malaria was not endemic.
You can observe evolution on much narrower timescales. People were following how covid was evolving after all. Evolution just means some changes to dna. Even identical twin children have some differences between them.
It's more of a function of selection pressure applied to genes per unit time based on some environmental factor, so you'd expect to observe less evolution in narrower timescales simply because it takes few decades for humans to pass on genes versus bacteria or viruses. In the same fashion, if some gene pool is locally optimal(?) against the environmental pressures, it may just stop evolving meaningfully. E.g, If male baldness were reversed easily with a pill or something, the environmental pressure to select those genes would decrease rapidly.
Another would be, 50k years is such a narrow window that evolution cannot be observed across it.