@WyrmSpawN
It might not have been long enough ago to make any difference there, if the unicorns remember that they’re supposed to have magic and Sunny’s dad knows that the pony tribes used to have healthy relations.
Though either way, if the pegasi managed to develop smartphones, you’d think they’d also have developed technology to properly compensate for the loss of flight magic (such as jetpacks).
It is possible that the earth ponies and unicorns also had the same technology as the pegasi, Izzy knew what a smartphone was and the remote control technology that Phyllis has in her Canterlogic is at the 2021 level; only communication technology is absent. While the pegasi continue to have smartphones, TVs and possibly PCs because they may have a large empire, it is possible that the fear caused the earth ponies to discard this technology while the unicorns may have two serious problems. First, magic and electronics do not go well together. Secondly, there were not many unicorns in the G4 who wanted “down-to-earth” work and expertise on how to take care of their technology.
The gap between Zephyr Heights, Maretime Bay and Bridlewood may indicate a time gap of at least thirty years from a human perspective of how long the technological decline had taken place. It can be very interesting to see how the technology can be in the other nine states, especially those on the east coast north of Maretime Bay / Horseshore Bay. The unicorns have been hit hard because they did not possess the skills needed, especially if Bridlewood may have been a resort for aristocratic unicorns from Canterlot who may have been evacuated when the magic disappeared.
I think Argyle found out rather than knowing it, he had left riddles because the lighthouse is more than what Sunny anticipated, and that he had secrets that his daughter was not aware of. The ponies had not forgotten that they could fly - could use magic, while the earth ponies seem to have forgotten their strength and ability to manipulate soil and plants. The latter may be the result of modern technology. This means that the ponies were exposed to memory erasure spells which means that only their instinctive memories were intact.
50-80 years minimum. Maybe less. 200 years at most. Things age just as fast on Equus as in our world when magic spells are not used. Zephyr Heights had not changed much, while the lighthouse in Maretime Bay had not been given a residential house - which appeared to have been built by Argyle before Sunny was born.
The movie has left a lot of questions, but one thing is clear; it was a hostile attack that ribbed the ponies for their magic, and it had happened “recently”. The ponies had not attacked each other. They had not lost their magic just because they had lost friendship with each other. This means that Twilight and her friends have not failed, their legacy was sabotaged and almost wiped out by a mysterious enemy.
Remember what happened when the memory stone was used in the EQG to isolate and force away the Sunset by creating animosity and hostility through manipulating the memories of people. That may be what happened to Equestria; but such a spell … the power behind it must be astronomical, almost at the alicorn level or higher.