This is an important point, especially for WDW vets who use FP+ and MDX there. So I am going to take this opportunity to elaborate.
As part of MDX at WDW, a reported $2 billion project, Disney built extensive wifi just about everywhere at WDW. It allows guests to use the Disney network with no need for cellular access.
At DLR things are different. It is true that DLR does not have wifi provided anywhere near to the level of WDW. Some have wondered why and some have speculated that Disney did not have a good way to keep it to Disney guests and keep out folks across the street, for example. This is a drawback especially for non-US visitors who do not want or cannot practically use their cellular service in the US. That would be a big reason that Disney has kept legacy FP available.
Hopefully some day this will change but it is reality for now.