This all comes from a student's experience as crazy as it sounds but I want to get to the point.
Mirage spots in ORAS are, looking back at it...fucking awesome. I have no idea why I never appreciated them as much as they deserve despite praising how you get the Mythicals in the Switch games.
If these games had came out before the Internet, I'm confident Pokemon's popularity would have gone crazy. Let me elaborate: they are the perfect playground rumour.
Take the Lake Guardians for example. Relatively easy to bump into them. But you can only catch one depending on the time of day. Kids may figure that out. It wouldn't be that easy, at least for the ones who didn't play the Sinnoh games, but nothing crazy. What would be a way more difficult task would be finding Giratina, since it requires trading extremely rare Legendaries. Still, just think about how "playground rumor-y" it gets: 《you need to be friends with 3 Pokemon in your team, then you have to catch 3 special little elfs at different days of the week, then you get a cool dragon who controls time or space, and if you have the two dragons from both games a cooler spooky dragon appears!》
But it gets crazier. For Tornadus and Thundurus, you need to have Castform in your team. Who would do that!? (I mean as a kid I did try in RSE because the form changing was wild to me, but the novelty didn't last long and ORAS already has Megas) and Landorus is another Giratina situation.
But then we get to the crowning point, the peak. Needing a level 100 Pokemon for Reshiram or Zekrom. THAT'S LITERALLY A PLAYGROUND RUMOR FUELED BY CHILD WONDER!" Children were obsessed with level 100 Pokemon supposedly unlocking stuff even as late as in Gen 4 days. This time it would actually be true.
As an adult, I find the whole system archaic and needessly complicated, just as I did as a teenager. But trying to look at it from a child's eyes...it must have been so awesome to play ORAS blind, specially as your first game. All these mysterious, strange Pokemon with their own music themes and obscure ways of getting them. Sure, you can argue that, as always, GF was late to the party and most players didn't have this experience, but the idea of it being a possibility is amusing to me.