It was a complete societal collapse. Language, skills, technology, medicine, academia, arts, etcetera just like totally gone and they don't even remember the name of the civilization 50 years later with only the elderly remembering it from their childhood. Rome is like a really well known example but they're actually everywhere and it's kind of spooky. It doesn't take very long for it to happen either
Technology: it was obviously largely based on functioning with, fabricated by, and maintained through creation magic and nothing else. The loss of creation magic just made it become Roman Concrete, flying statues, and Greek Fire etc. Everything would collapse from there. It would be like losing the knowledge to fix the electrical systems or running water that we totally depend on. You don't know how the things you tale for granted work. Like, "How do magnets work". Totes distressing how many ppl just don't understand basic science. The thing that Hydalyn did was force that kind of collapse to happen to remake magic with dynamis in mind, while the Ascians accelerated technological and magical studies growth past what society could have done alone for nefarious reasons. An, that created more collapses with tons of super dangerous result that we like happen to just come across at the right time (all raids, Shinryu, ascian ruins, elder primals)