The Declining by Degrees concept isn't a single thing, but rather a conflation of multiple things (a slow dying-off of several dozen intricate details in every visual sweep, stuff no one notices consciously, but given enough volume really makes it immersive). In exactly the same way, the CAUSES of declining by degrees is a conflation of multiple variables.
Are the WDW execs clueless? No, they are reasonably smart people who can play a political game. The reward structure in place is tilted toward doing more Declining by Degrees, frankly. Hit or beat your quarterly goals to get a personal financial reward. It's TOP leadership - CEO and parks guru - who can change that. And, at the end of the day, it's the messaging to Wall Street analysts that matter the most. If you weaned those guys off short-term growth year over year, we'd be having a whole different conversation. That starts and ends with the CEO (and maybe the CFO, not to mention corporate strategy), not the park vice presidents.
Culture. It's definitely true Disneyland has a culture WDW does not. There is pride in those who work in the park Walt built and oversaw, walking the same places he walked. This isn't a matter of "education" per se, though some of that would help (see below). In the meantime, culture change is extremely hard. Not for nothing are most business book bestsellers ultimately about culture change.
Worker education. For the first 30 years of its existence, Disneyland paid its employees a massive premium when compared to local competition and industries. This did two things. First, it made people want to stay and become "lifers"--guess where that aforementioned culture comes from? Second, it made the hiring extremely competitive. Only those who were super-friendly and super with-it actually got hired. It's true that DL no longer pays that much (comparatively), but the big thing that sticks out in the case of WDW is the source of workers. Giant herds of front line CMs are on the college program or the International program (especially in Epcot for the latter). Giant herds. On the one hand, this creates a lot of turnover that can actually be beneficial: when you've only been there for six months, you're less jaded and the smile is more likely to be real. This is someone who believes in the magic. On the other hand, the more experienced CPers and IPers around you ARE jaded, and eventually you feel it too. This, too, is part of where the culture comes from.
I'm tempted to say that WDI on both coasts is the only place firing on all cylinders, but that's not entirely true either. The place is VERY political, to the point where the project, the outcome, and the guest experience take backseats to ensuring effective politics within the halls of WDI, and that's a crying shame since the folks involved are so talented (and WDI folks really do care. I'm not sure I've even heard stories about those guys becoming jaded).
So can a visit to Anaheim fix things? Maybe it'll move the needle a little bit. Much more potent would be an adjustment of the reward structure for executives, and finding a way to create the right culture among hourly CMs. The old Disneyland formula worked well: pay so much in hourly wage that you definitely fall in line since you want to keep the job so badly. But that requires massive vision to bring about, and it involves the corporate suite in Burbank, not just the park presidents.