Worst change in ten years? Easy. The implementation of the 180+10 ADR system. All spontaneity has been removed from the ability to get a decent meal. If you care at all about dining at Disney, you now have to plan your vactions more than half a year in advance. And even worse. Not only do you have to figure out that you are going to WDW more than half a year in advance, you now have to scour the internet to find reliable park opening times and EMH schedules so that you can plan which park you are going to visit 6 friggin' months before you actually travel. Heaven forbid you land that coveted table at Cindy's Castle 189 days before departure, only to decide two weeks before you go that the MK is not really a good park to visit that day. And when you score that table at Le Cellier at 5:15 for dinner, you are pretty much committed to touring Epcot that day, like it or not.
Planning a Disney vacation is a lot fun, no doubt about it. But we all know that our park plans influence our dining choices, and our dining choices influence our park plans. But do we really have to make these decisons 190 days in advance? The fallout has been three-fold:
1.) It has caused people to double (or triple) book ressies, which in turn makes getting ressies even harder;
2.) It has made it next to impossible for local residents to dine at the nicer restaurants. (Do you make dinner reservations in your home town 180 days in advance?); and
3.) It has removed almost all chance of flying by the seat of your pants while doing a Disney vacation. Try to walk up at the nicer restaurants and you will be turned away in favor of people who uber-planned their trips more than 6 months in advance, leading you to the conclusion that if you can't beat them, you must join them. And when everyone "joins them", it turns planning a Disney vacation into a strategic coordination effort that rivals planning the Normandy invasion.
I've been taking
Disney vacations since the first summer they were open (1972) and have been back almost every year since, at least once a year. Planning a trip has never been so complicated or stressful as it is now, and I attribute a lot of that to change over to the 180+10 system. 60 days for on-site guests and 30 days for everyone else was just fine. It didn't need to change.