Barriers no doubt do matter, but in any given race and apart from all of the above generally sound reasons mentioned in posts, a combination of luck in the running, fitness and split second Jockey decisions for all a race's runners [not just one] and how they effect each other, will make fools of any attempt to find 'consistent' simple answers to what will or won't be good or bad barriers for any given race. 'Perceived' bad barriers [better odds too] often turn out to be good barriers and vis-a-vis.

Like any aspect of horse racing, there are guidelines for just about anything that a punter wants to consider, but in the end they are so often wrong that they will never put a long term profit in our pocket.