Wasn't the whole point of the ticketing system (originally) just to get people riding the rides they may not have otherwise opted to ride and to limit the rides on the most popular rides? An original Disneyland ticket book would contain a pretty large number of A and B tickets, with fewer C and D tickets, and only a small number of E tickets. The expectation was that the E-tickets would be the most popular/lowest capacity attractions and to keep the lines from getting too long, they limited the number of times you could ride the popular attractions. If a ride didn't get much riders or was super high capacity, they gave it an A ticket because people had tons of A-tickets to use. Like today's FastPass system, you spread out the lines and prevent the popular rides from having insane lines while the less popular rides send out at well under capacity.
As such, matching "quality" or length of a product to it's ticket level is essentially irrelevant and an attraction that opens as an "E-ticket" could fluctuate to a "D" or "C" ticket over time if it has high enough capacity and the interest in the attraction wanes. An attraction like UoE or County Bears (if Disney still used a ticketing system) could easily be an "A" or "B" ticket attraction now simply because they have such high capacity and low demand.