This is terrible, and reservations sound very necessary here. But why don't they have any kind of traffic control at the beginning of the canyon? Crystal has only had to deal with full parking and people turned away since last year, when they went on Ikon, but after a few days of people being furious they partnered with the DOT to put up electronic signs on the only road in and about 50 minutes away, so that people could turn around well before they go there if it said "parking full." (They would estimate based on how full the lot was and how many cars they thought were on the road). With only 12 miles and one road in a canyon, it seems like it would be really easy for the resort to estimate when parking would fill up then turn on a sign.
Honestly - they do have some traffic control, it's just... inconsistently managed as far as I can tell. (And talking to DH last night about it he says last year was better with this than the year before, so that's progress, I guess.) One of the huge issues with traffic is 2WD vehicles sliding off the road and creating gridlock in bad weather, when they have clearly marked signs at the base saying 4WD or chains only when it's snowing or forecasted to snow. Sometimes there is someone at the base checking vehicles and only allowing appropriate ones up... most of the time there isn't. Lots of folks take their chances (especially in rental cars) and it creates a mess. I suspect a large part of the problem is people being overly optimistic. Yeah, it says the lot's almost full and there are hundreds of cars in front of me, but I'll make it! In my 2WD car with bald tires...
They do also send out text alerts and twitter alerts when lots are nearing and at capacity (admittedly this could be part of DH's problem, because I had to install twitter on his phone for this purpose....) and have signs at the base and all the way out on the interstate, but only close the canyons to uphill traffic when the entire canyon is full. They allow parking on the sides of the roads and there are 2 resorts, and there is public access (backcountry/non-ski resort) parking and hotel lots and that type of thing, so it's a bit of a mess guessing which cars are trying to go where, I'd imagine. Declaring a specific lot to be full is easy enough and they have parking staff to do that. I don't know the details of how they determine "CANYON FULL" but I'd guess part of the issue is that there is probably a few parking spots available SOMEWHERE, so there are people milling around looking over several miles or waiting for folks to leave.
Just throwing out ideas, but they could have online reservations tied to your ski pass AND put in a pass sales kiosk and a pass reader for those without passes at the base of the canyon and you get a reservation to park at whichever resort lot you've reserved or for the backcountry access parking or hotel or business you're visiting up there... Haha, maybe somehow tie it to driving a vehicle with appropriate tires for storm days while I'm wishful thinking....
Interestingly, DH hated this whole idea (he prefers time travel to 20 years ago as his ideal solution...), but he conceded that if he knew he'd have a parking spot waiting (even a terrible parking spot), he'd pay good money for that. His concern was that they'll take reservations, but not enforce them and therefore you could have a reservation AND no parking spot. Which would be the worst of both worlds... Hence my whole "gotta have a pass you can scan to get into the lot" idea. And really, we should be figuring out how to entice people to ride the ski bus more often... so there is that too. But that's probably a really difficult sell with COVID....
And back to the original COVID part of this - with a well managed reservation website, you could handle reservations to limit skiers on the mountain well, even with some flexibility. Paying for in-canyon lodging or maybe in-town lodging with reserved tickets? you automatically can reserve a lift ticket reservation for each day of lodging. Don't want to ski that day? You release that lift ticket reservation and it opens up to the public. Even last minute in the morning or mid-day - there would be locals who could pick it up. Maybe your season pass comes with a certain number of days of guaranteed reserved skiing and the rest are a lottery, plus last minute pickups from released reservations, etc...
Anyway, obviously I'm just rambling about possible ideas. But it's feasible that for extra busy resorts, they come out of this better than they were because it forces them to come up with plans for limiting attendance in a reasonable way that could make it a better experience. Until someone invents time travel...