Fast Pass is an option, not a requirement. Life's about choices. Choose to use it, you have to follow the rules for it. Otherwise, choose stand-by that fits more into your schedule of dinner arrangements and what not. If you don't like the length of Stand-by, then don't go on the attraction or come back when it is to your liking.
If the time you get to the machine doesn't fit in with your schedule, don't get it. If it does, get it.
It's really not difficult to actually keep to the window on it. All phones have an alarm on them. Set the alarm a bit early. It goes off, decide what your next step is. Continue what you are doing or go to the attraction and use the FP.
It's neither here nor there that they are now enforcing it and didn't in the past. The current rule will be to come back within the window. If you choose to use FP, then you have to play by the new rules.