Just because us humans don't have access with infinite accuracy to initial conditions doesn't mean that initial conditions don't exist with infinite detail. Our human inability to accurately predict doesn't mean that, for example, weather doesn't happen deterministically, just that we are limited weather prognosticators.
However, true randomness in quantum events would, agreeably, kill determinism.
Just because us humans don't have access with infinite accuracy to initial conditions doesn't mean that initial conditions don't exist with infinite detail. Our human inability to accurately predict doesn't mean that, for example, weather doesn't happen deterministically, just that we are limited weather prognosticators.
However, true randomness in quantum events would, agreeably, kill determinism.