You can arbitrarily pick any date and all it a "real" extension. I find 9 months is pretty darned real.
But it's not 9 additional months because the parks aren't open for those 9 months. Assuming the parks open by July sometime (and that's still a big IF), that's only about 5 months to use the extension. You think it's reasonable that all the people from April, May, June, and half of March should be able to turn around and get PTO approved, book affordable flights, arrange affordable lodging, and make the trip, within that 5 month period - along with all the other people who were already planning trips from July through mid-December? Given how full the resorts and parks are anyway, and the reduction in capacity that's coming, all those people probably wouldn't be able to fit into the parks, even if they wanted to. I am also from a state that has a travel restriction to Florida, so until that's lifted, I would need 3 weeks - the first two for quarantine before I could go to the parks.
Plus, people make travel choices based on price all the time. For many families, if the flight, hotel, and ticket deals don't align, they don't go. It's easy to tell someone just to suck it up and pay more, but for a lot of people, changing dates means paying more anyway because there's a good chance they lost a promotional/discount rate for their resort. And if someone was making a trip to stay on DVC points, they're really screwed. They might have booked a studio or 1BR at their home resort at 11 months, and now they're short points because those lower-point rooms are gone or there's just no availability for the remaining weeks this year. So people get the choice of paying more for their tickets next year or paying more for their lodging trying to go before December 15. Either way, you're pricing people out.
Also going by your theory if people move to a cheaper date they shouldn't get a discount from Disney. They should just move the dates, and be happy.
People moving to a cheaper date DON'T get a discount from Disney. If you buy tickets for Christmas or Easter, cancel, and reschedule for the following August, you don't get the additional money back because you're going at a cheaper time. Disney always charges more if you move your tickets to a more expensive date, and keeps the money if you move to a cheaper date.
There are lots of people who can (or will) only go when school is out of session. Many of them paid high
ticket prices to go during spring break or Easter this year, and now to reschedule within the extension they really only have late July (if it opens) or possibly part of August (depending on how early/late their districts start). None of them are getting refunds to go at a less desirable time. In fairness, they should get to go during a similar time in 2021.