First off, for me at least the bus issues aren't a problem. I'm in super-zen-relaxed mode when I'm up at Disney, and in absolutely no rush to get anywhere or do anything. I drive up to Disney and have my car available anytime, but rarely ever use it. So I'm not commenting from a position of frustration...just interested to follow the issue as others are posting about it.
Secondly, as someone who goes to Disney 30-40 day a year or more, and going consistently since 1971, I've had a pretty good ringside seat to all the various fluctuations and changes to Disney's transportation system...even from month-to-month or in different seasons. In general, I would agree that I've seen a slight decline in bus timeliness over the long term, but in the past 5-7 years, I've had mixed results on wait times that have not shown the recent months to be any more drastic than the worst wait times in the past decade or so. Taken back 20+ years, I think the schedules have become less reliable...and in the past 5 years I'd say the frequency of longer waits over shorter waits seems have increased.
Third - in general, bus service is equally good and/or unreliable at all of the Disney Resorts. Having stayed at all of the Disney resorts from values to premiums, I've had days at each resort that were lucky with fast bus arrivals, and days with bad luck and 40 min + waits. While the resorts with lots of stops sometimes seem worse, to me they seem to have more busses running their routes - so heavy crowds and lots of stops are balanced by more busses...while resorts with dedicated busses tend to just have less busses operating that route, and therefore often have longer waits but less crowded busses. Tit for tat. The only resorts that I would consider to have an advantage in transportation would be those that have proximity to a park or alternate transportation options such as boats. Their busses aren't any better, but at least with one particular park there is an alternative method to get there.
Fourth - Remember that no matter how 'on-schedule' the busses may start the day, it is nearly impossible to keep them that way. Having the busses spaced 20 minutes apart is a lovely theory - but the first time a bus has to load a handicapped person, it will fall 5 minutes off schedule...and lose another 5 minutes every time they have to load and unload passengers requiring assistance. And the next bus will seem to arrive at the stop just minutes apart from the first. But now if two busses are circulating on that route, it's going to be much longer for the next arrival. This cycle continues throughout the day, throwing all the bus schedules out of whack, and requiring constant adjustments throughout the day to try to reroute busses to other routes that are experiencing severe backups. And pulling busses from one route to another busier one might leave a handful of people on an uncrowded route without their next bus rerouted and a 40-minute wait for the next one. And so on...
Fifth - With some gambling and some luck, you can find creative ways around the bus problems. There are no guarantees it will always be faster, but it can work. At Saratoga, you can walk to Downtown Disney and catch a resort bus from there that is close to the park you are visiting - then use boat transportation or walking paths to get to the park. For Epcot, jump a Boardwalk bus, and walk in. For Magic Kingdom, catch a Wilderness Lodge/Contemporary/Polynesian/etc bus, then use boat, Monorail, or footpath to get in. Same goes for coming home...leaving Epcot after watching illuminations, it can be faster to walk out to Boardwalk and jump the Downtown Disney bus, then walk to Saratoga. Sometimes, it may not be faster, but it might be less stressful - I personally enjoy the Magic Kingdom area boats to and from resorts as a relaxing and scenic ride that helps keep the magic immersion alive - so on my way to Magic Kingdom from OKW or Saratoga, I'll often start my day by boating over to Marketplace (another lovely ride), then bussing to Wilderness Lodge where I walk through to the back to catch the boat to Magic Kindgom. I am likely losing some time in this wayward route, but I've already had two lovely boat rides and an uncrowded bus ride, so I'm relaxed and in a good mood when I hit the Kingdom. If a HS bus arrives just as I'm walking up to the Saratoga Springs bus stop and I'm going to Epcot, I might just jump on that HS bus, then walk over to the boat launch at HS to take the slow and relaxing ride to Epcot, where I can walk into the World Showcase area...especially useful if I'm headed to a lunch there as I won't have to walk through the whole of Epcot to get there. You get the idea!
Anyway...that's my input. I agree things seem to be a little worse overall, and probably not getting any better. And if I had a reservation for a meal at another resort, I would in that case jump in my car to head over rather than rely on the busses. but the majority of the time, I do use Disney busses, but just keep my schedule loose, my expectations low, and gamble and experiment a bit with different routes and methods to get to where I'm going!