I think Russell is fairly clear in this passage --his gripe is not so much with Aristotle, but with how (in his opinion) Aristotelian thought continued to dominate the fields of science, philosophy, and logic long after it had outlived its usefulness.
In particular, he saw the field of logic as having ossified for thousands of years after Aristotle's death. As one of the leading figures of a movement that ushered in a new era of a radically different and advanced approach to logic, he would quite naturally have viewed the fact that two thousand years passed without significant advances in his field as a crime against human potential.
The modern dethronement of Aristotelian logic, although long delayed, was so successful that it is now difficult to imagine how stiff the initial opposition to innovators like Russell and his immediate predecessors must have been at the time.