i just thought of something: what if opaline is the reason why other species had vanished without any trace of them, including the dragons if she was using them to gain more power?
There are two puzzles, applicable; the first is where all the monsters from G4 are, we know these were common in Equestria and were created by Grogar - and the first is where all the non ponies are. It is possible that these two riddles are one and the same; and that it happened when Equestria collapsed.
We don’t know why the dragons are gone, Sparky is proof that they still exist. They may have been evacuated out of Equestria which may have been quarantined by Spike. They were last seen a few generations earlier according to Zipp, probably just after the magic disappeared. We don’t know why non-triotribe ponies like sea ponies and crystal ponies are gone, they may have fled and may have also done the same as Spike. We don’t know why the kirins and changelings have disappeared, but they can manage in a world without active magic as internal magic will work, like the nirik magic in the kirins and the emotion sucking in the changelings.
Then there is only one logical answer to this; Equestria was quarantined, but it’s also possible that we simply didn’t see non-ponies because the G5 writers were lazy. We have only seen three specific locations in Equestria, and C3 has shown that the makers are struggling to present the world in 3D, maybe it should be in 2D?
But we will find out, the map for C2 has revealed that we WILL discover sea ponies in the first season, likely in C4. Sunny and her friends can find out if Equestria was quarantined by interrogating the sea ponies.
And the many rumors about the G5 world that had been aired before the movie are interesting - one of these is that an early villain will become a member of the new Mane 6 - and that has been confirmed with Misty. Some of the rumors are that Equestria has been split into different realms from high-tech changelings to karate-obsessed kirins. Someone makes these cell phones in the G5, it will be impressive if it is the changelings.
Opaline was stripped of her magic centuries early, and there is nothing connecting her to Equestria’s collapse that hasn’t been mentioned in C2. Sunny, on the other hand, thought the tribes split up after Twilight took their magic, we know a little better. Argyle and Sunny were not very open about what happened to the non-ponies, even though much of the collection in the movie came from exactly these non-ponies. Hologram-Twilight didn’t accuse Opaline of being anything but a magic thief and usurper.