Um, YOU need to take responsibility for YOUR choice not to look at any of the signs which have the closing time on it. You went by at least two signs which said that the park closed at 8. Should the park have an employee out with a bullhorn alerting everyone that it closed at 8?
By the way, I always assumed that the reason the park closed early during post-season was that the lines are usually shorter, so you'd get the same amount of rides in that you would had the park been 10-10. I don't know if that's actually the reason, but I can certainly say I get on more rides during a 10-8 day where the park is empty than I would have had the park been open 10-10 but been busy.