I'm not so sure. Keep in mind that ADA doesn't require that you provide everyone with the exact same way to do everything. For example, a taxi company doesn't have to equip every cab so that it can handle every disability that might be encountered. It is OK for them to only have part of their fleet equipped for various disabilities, and dispatch those when someone needs one.
With Domino's case, you have a lot of variations the customer has to choose from, and a lot of information that is on the website that would be slow and inconvenient to deal with by phone. Nutritional information, for example. It would be quite the hassle (for both the customer and the person at Domino's) to get nutritional information for all the options a customer might be interested in. I've spent 20 minutes at times fiddling with the build-your-own options checking out nutritional trade offs--that could have taken hours on the phone!
Domino's also usually has a ton of coupons available and a bunch of different specials. Dealing with all those over the phone would also take a lot of time.
Compare to a prescription refill at a pharmacy. There generally all you need to do is communicate your prescription number to the pharmacy. A phone refill consists of calling and when they answer saying "I need to refill prescription #NNNNNNNN".
I think it is quite possible that courts will ultimately agree that for ordering a prescription refill, at least at a pharmacy that hasn't gone overboard with coupons and deals, providing phone ordering is sufficient accommodation for blind people but for ordering pizza at a place with a large menu that has a lot of customization options phone ordering is insufficient accommodation.