This is not extra, this is what was available before Fastpass without paying extra, I expected no less accommodation after Fastpass was introduced and yet they have failed to do this.
Was this "an accommodation" that DLR provided for you previously? Or was it just that you (and anyone else) were allowed to access this area early and lay out a tarp? I don't believe an accommodation has been taken away -- it sounds more like access to a specific location is now denied to everyone, with or without disabilities.
I understand your frustration. I really do. Something was previously allowed and now it is not. But it's been denied across the board. Accessed only for those with a FP or those paying. It has nothing to do with disabilities or taking away an accommodation.
I don't believe the ADA requires a venue to create a "less crowded" viewing area, especially with prime views added in, not even for a service dog. Even the
DAS does not guarantee a guest won't endure crowds during their wait for a ride. You as the dog's owner are tasked with determining whether you believe a situation is safe/appropriate for your dog. I suppose a small dog could be held, by the owner or another in the party, creating a safer environment. A large dog could be placed between you and other members of your party, creating buffer space and preventing others from inadvertently stepping on the dog. Arriving early and placing yourselves against a railing or wall might offer some protection. Those are all options available to you and your dog. Maybe not ideal, but options.
You've mentioned quick exit, but that's not necessarily something that must be provided either. The options I see are to be in a less crowded area and subsequently have relatively easy exit, but it may not be the best viewing spot; or you can be in a prime viewing spot, but expect it to be crowded which also likely means more difficult exit out of the crowd.
My experiences at WDW have always been that a mobility device is required to access to roped off "handicapped" seating/viewing areas. And they further restrict how many companions may be with you in that area. People on
ECVs or wheelchairs are parked close together, almost elbow to elbow, with companions either sitting in front or standing behind - not beside you. If you experienced a "roomier" situation, chalk it up to a low-crowd day and not that the space was guaranteed.
You are certainly within your rights to write to Disney and explain your situation. But I'd be surprised to find spacious areas reserved for 60% capacity. Disney is a crowded, popular destination. You and your service dog are allowed to enter the gates, ride the rides, watch the shows, eat at the restaurants. However, it's up to you to determine whether any of those situations "work" for your needs. Preferred accommodations are not legislated, equal access is required by the ADA. Unfortunately there is no way to guarantee for equal experiences.
I hope you do find a way to enjoy future visits to DLR!