When Alton Towers went down the theme park route it was obviously inspired by Magic Kingdom's method of getting to the park. However unlike Alton Towers, Magic Kingdom has an even worse problem with the only way getting there by a very slow boat, train cars or a monorail system. You can't do the walk unlike Towers. Considering that park has 70,000 people on average getting there way to the park, Alton Towers monorail problem seems so much more irrelevant. It's 12,000 on average a day seems rather small fry. Besides those 12,000 people won't all be arriving at the same time. I've been visiting for years and I've never waited more then ten minutes for the monorail.
I think the monorail is a great way to get to the park as it helps stagger people getting to the entrance, gives you a sneak peak onto your day and allows less over-crowding at the entrance and on any hand, if 3,000 PPH is its absolute minimum then it must be able to get through much higher when it has more trains going round.