You will be in for some LONG waits if you stand in line to order at the (usually one) register that is open. Some places are mobile order only, like the Cozy Cones that sells ice cream and the Tiki Juice Bar. Sometimes the ice cream parlor on Main Street goes to mobile order only. And some places don't offer mobile order at all, and lines are long at those (Adorable Snowman treats and Rancho del Zocalo, off the top of my head).
Honestly, you will not be on your phone "all day" using mobile order. It literally is a process that takes a minute or 2 to place the order, then just clicking a button when you are ready and waiting for a notification. It's FAR faster and less effort than standing in a line, ordering, paying, and then standing in line again at the counter to pick up your food. The mobile order process is working like a well oiled machine at this point with the majority of cast members at each location dedicated to fulfilling those orders specifically.