True randomness is a slippery thing: It is a property not of things in themselves, like individual numbers, but of their relationship to one another. One number is not random; it only becomes random in relation to a sequence of other numbers, and the degree of its randomness is a property of the whole group. You can’t be random, in modern parlance, without having some shared baseline of normality or appropriateness to measure yourself against. Randomness is relational.
The problem modern computers have with randomness is that it doesn’t make mathematical sense.