I just got an idea! Might have been mentioned already, but I love my idea so I'm going to talk about it anyway:
Why not charge the Key holders a discounted daily ticket price for days they are not blacked out but have no reservations available? I think it's fair to charge, say, 1/4 of the current ticket price. Like if currently the day tickets are $160 per day, the Key holder will pay $40. That way, they can still go to the parks any time they want (excepting their Key's blackout dates), with a free reservation or paid discount ticket. If they don't want to pay the extra, they can wait till their reservation comes in. If they want to go on a blackout date of their Key, then they pay full ticket price. That way, Key holders won't just drop in any time, but they can still do it any time they aren't blacked out without paying full day ticket prices, which makes no sense when you already have a Key.
My plan will increase your revenue while remove customer dissatisfaction about the new key system, and increase Key sales. Because right now, potential Key customers are definitely holding themselves back reading about all this "nightmare" news.
As far as controlling crowds go, there's only one way to control crowds: increase tickets price. I think Disney would have had a better customer response from raising prices significantly than from blocking them out unexpectedly, though the final effect of both are the same: in both cases, fewer people can go to Disneyland. But in the current situation, Disney is making less money while enduring more customer dissatisfaction, as the customers are feeling like they are not receiving what they thought they paid for.