I agree the area around Good's To Go is too cramped for effective social distancing to make mobile ordering viable there. They could, however, do it if they'd set up an area only for mobile pickup. It would likely require at least some additional employees, a runner to bring the food from the prep area, an employee to supervise pick-up, and an extra prep person or two to keep up the flow of orders, in an already cramped space. Plus some way to keep hot foods hot and cold foods cold, while not impeding/bottlenecking an area during the pandemic. But would it be worth the cost long term? Let's say they did do this, Olivia's outdoor patio seating area would be a good location, but would still require some modification for efficient access, pouring new concrete, removing part of a fence. Then running power for refrigerators and warming equipment. This would also remove some seating from a popular restaurant, all for a pandemic where we can finally see the light at the end of the tunnel as vaccines become more widely available...though it would still probably be useful for the next 9 or 10 months.
I'm guessing that is a cost that Disney does not want to simply absorb given their current position. Especially given it is relatively easy to just use the current location with social distancing markers, which limits the number of people in the area, and gives staff time to better prepare orders between guests.