Actually, this "policy" you keep quoting, was never the official policy. The OFFICIAL policy was the one that is currently being enforced. What changed was the enforcement of it. They could have chosen to begin enforcing the policy again at any time. With the FP changes on the horizon, it was necessary to do so. Otherwise, the FP line would have evolved into a new standby line.
And yes, I'm sorry, but it is poor planning on your part. You know weeks or months in advance what time your ADR's are and what time you want to get a seat for a particular experience such as Wishes, MSEP or Fantasmic. Therefore, if you get to an attraction and the window being offered falls in that period and you still get one, it is your own fault due to poor planning that it will no longer be accepted. Forget about the old enforcement. This is the new enforcement and it will not change.
You don't have to like it, but it's this same sense of undeserved entitlement coming from so many guests that drives me insane. Quite frankly I don't care how much money you paid. So did every other person coming in the FP line during the correct window, yet it's always that one person who seems to think that because they shelled out thousands of dollars they're automatically entitled to not follow the rules. To them, I say, take your money elsewhere if you don't like it, and good riddance to bad rubbish.