There are so many sides to this that it's really difficult to reach a decision that would please everybody.
Universal has limited land, so if Universal can put people off not driving by enforcing a a charge, then it works in their favour by having people stranded on site which is perfect for Universal. As somebody who's always going to be driving, I find it incredibly annoying but I have to respect that I have a choice to drive and if I don't, I can save myself some money.
On the other hand, if Disney enforce this, it's something completely different. For a starter, they're going to charge for something that has been free for a long time and they offer no chance to opt out of it. Some of the features will remain free for people staying off site and some of the other features are a one time payment which you will be paying the same for daily. Disney have so much room, that paying for parking is really a slap in the face.