Everything is a factor I'm sure, but the mobile device itself is not going to be the bottleneck between the device, controller and drone.
In my observance of many years of threads it actually does in quite a few instances. (As in probably 1000+ reports). As to all in this thread, those who haven't been in the DJI loop since almost the start, skipping P1 and
P2. DJI came into it's major leap with the release of the Inspire 1 and then months later with the Phantom3Pro/Adv. Both (all three actually) were sold with the announcement of "Smart Flight Features" or now smart shots. But as worded most were greatly disappointed to find out that they could not do them out of the box.
It was then that the Announced SDK for those 3 models was open for third party developers. That was the time frame for many companies to be born. In the subject for this discussion Litchi was born. It opened the world for many to do what they couldn't do with stick control.
But DJI then reversed and started releasing firmware with the flight features with the caveats mentioned, as said fly first for instance. Litchi had the shortest learning curve and if memory serves was the cheapest of all offerings. So Litchi dominated the market as 3rd party DJI flight software.
Litchi has and continues to be in constant communication with DJI with their SDK releases and has been totally transparent in what DJI releases, it's bugs and omissions unlike DJI itself which honestly IMHO is closed minded and as mentioned is all about money.
I haven't researched the release date but DJI did announce more than a few aircraft releases ago, that waypoints were discontinued on consumer products. So anyone who bought after that "Should Know" that that feature set isn't included nor would be supported at the level it was.
Yes I don't have a dog in this fight as to the Air(S) not having waypoints built in or how Litchi works with them, nor any other release that uses the Fly App. But I do know that I had dropped into upgrade mode of my P3P to get a Air when it was introduced. I then did a bit of research and found that other than a folding drone, My P3P was still IMHO, a much better drone fit for me. To me the Fly App is still greatly inferior to the Go 3 and Go 4 Apps, although they have made strides to lock it down and give users what they "Demanded".
I did however weigh the market heavily and found that the
Mavic 2 series provided what I would need and wanted even though it was coming up on it's third anniversary of release. Now my 4 year old series Drone seems to be what people of this thread want but can't have. I even looked at the
Mini3 Pro lately, but other than a sub 250g...which doesn't affect me anyway... I'll just keep flying, filming, and taking stills with my P3P and
M2Z (With
SC). I am free of DJI's limitations and nannyware and all the hype that it seems is just a rehash of what we went through back in the P3P days...Best of luck to all new DJI owners, but I think I will just stick with my tried, proven and "Perfect" (Bug Free) air-frames and Firmware of days gone by, all that fly perfect IMHO with Litchi, which BTW, that I have had for over 6 years.