If I may add into this conversation, I think it's also important to note how of all the fantasy creatures listed (unicorns, gryphons, dragons, wyrms, ect) unicorns are the only one inherently assosiated with young girls. At least here in the west. Which most certainly feeds into the infantalization because western cultures fucking hate young girls sksgsjsgjsgs, this could also lead to people being shamed for assosiating with something so "juvenile", expessially if the individual is masc aligned in any way. But now I'm just spitballing
That's probably part of it too. I feel like the shift started happening in the 80s?? That's where depictions like these really began popping off
While these depictions don't feel infantile, they're still clearly feminine. I wouldn't be surprised if their arrival was somehow tied to My Little Pony, though I don't think we can really point at a single source for their origin. It's just as likely that The Last Unicorn or Legend helped kickstart it.
Prior to the 70s, at least, it was very common to use unicorn iconography in logo design and art. Up here in Northern Europe, for example, it was very common for pharmacies and pharmaceutical companies to advertise themselves with unicorns
But since they became "a thing for girls" I feel like that trend has ended. It's most obvious with companies, but even with pharmacies, most of the ones I can think of use lions or birds or just a simple caduceus or asklepian to advertise themselves. I'm certain it's directly tied to the way horses have become "girly" in Western society since automobiles took over. Check out this Reddit thread for one perspective on it: https://www.reddit.com/r/AskHistorians/comments/dgho1d/when_did_horses_become_a_thing_for_girls/
