The issue with this is that for most of that time period, the increase in price at the very least didn't involve a decrease in what you received for it and sometimes actually involved getting more.
That doesn't appear to be the case going forward (adding parking fees to the resorts, the dramatic increase in upcharge events, etc.). There's a pretty big difference between charging someone $150 for what they used to get for $125, and charging someone $150 dollars for less than what they used to get for $125.
If they keep devaluing the standard experience while charging more money for it, it becomes far more difficult to justify paying the increased price.
I get what you mean. But Disney isn't necessarily "decreasing what you receive" -- for the most part, they are just making you pay more for it, but they are also slicing up the pricing.
Instead of a park ticket that can take you from 8 am to 10 pm... You can buy "Extra Morning Magic" from 7:45am - 9:00 am, the "regular ticket" for 9-6, and the party that goes from 6pm - 11 pm.
So you're not "getting less" -- You're actually getting more... if you are willing to pay separately for each of these pieces.
And this isn't a very new trend for WDW. Expansion of parties and paid events has been going on for several years. Reduction of EMH has been going on for several years.
10 years ago, the dining plan included appetizer and tip. While more than doubling the price, they have cut out these inclusions and substitutes less costly elements (resort unlimited soda cup, alcohol).
You mentioned the elimination of free parking.
So "less included in base price" isn't new. Though the pace of the change may be increasing. You are correct in the sense "receive less for base price"... but WDW is indeed expanding way to 'receive far more.. but be prepared to pay far more than base price."
And getting back to my original hypothesis -- Yes, this makes it more difficult to pay the increased base price. But that's it, WDW doesn't care so much if they lose some "base price" guests, if they are getting additional "upcharge" guests.
It's fair to say that 1 "deluxe resort on-site free spending family" is more profitable to Disney than 5-10 "off site budget guests."