I'm not sure I'd categorize Disney as going downhill either. We are AP holders, and spend several weeks per year there as well, so as regulars we've noticed changes - some positive and some not so positive:
Dining - Used to eat 2-3 TS meals per day, but not anymore. We did the regular DP and DxDP a few times, as hubby wanted to check them out, but we much prefer TIW (DDE). I will though say, that food and service have gone downhill over the years. Not sure if it's the DP, but after having eaten at pretty much every restaurant on property, we've noticed a decline in TS dining.
CMs - Have noticed a change in tone and attitudes with CMs as well. Have witnessed rude behaviour to guests, talking about guests aloud, complaints, etc. Some CMs seem downright bothered by guests, and this is not acceptable at all.
Prices - Prices go up, and quality goes down. Have already discussed food, but merchandise is another. Oh, boy! The quality of Disney merchandise is horrendous. But, people continue to snap the stuff up, so I can't see this changing anytime soon.
Surcharges - Fees and surcharges are a big pain.
This year, dining surcharge/upcharge for the summer was 1st week of June - Aug 15 (OP's dates were incorrect, as they change each year). We have no choice but to pay them, as we use TIW, and character meals are important to us, as we have young kids. Disney though doesn't advertise them at all, and just hits the guests with higher meal prices. We saw people leave their ADRs as they chose not to dine there as the higher meal prices were out of their budget.
Cleanliness - Have noticed a decline in this area as well - washrooms, parks, resorts, etc. Our DVC housekeeping is sometimes horrible, and this is an area that I've seen get worse over the past few years.
Overall, we continue to enjoy our Disney vacations. As DVC members, and AP holders, we go with the flow, but we have noticed small declines or changes over the years. I wouldn't categorize Disney as going downhill though, as they have improved in other areas, by adding new and exciting products or events that weren't there before.
I think Disney is continually evolving, and some issues are positive, whereas others are negative, but I wouldn't say Disney as a whole is going downhill or in a bad state.
Tiger