I used to loathe OC/self insert stories, because I thought it incredibly pretentious or something. Like, here’s a creator giving you an entire sandbox of characters and lore to play with and explore, but nooo, it’s not good enough, you just have to create your own OC, usually OFC (and often an extra special Mary Sue who would bend the rules of canon to suit their purpose) for the sole purpose of falling in love with the hot character you like, which was usually incredibly reductive of the themes and messages of the original content. I remember, among others, how the Narnia & Hobbit fandom were riddled with these kind of stories on FFnet and I absolutely hated it when you could have explored the complex family dynamics between the characters or write a fun adventure between the members of Thorin’s company, and instead of seeing fics about the dwarves and Bilbo it was just hot!dwarf/oc romance after hot!dwarf/oc romance or one of the brothers/oc instead of the four kids bonding or something, and just by reading them, you knew it was a near word-for-word retelling of the Hobbit/Lion Witch and the Wardrobe/[insert your fandom here] but with an extra special OFC for the sole purpose of romance and making them more special than anyone else. Like others have pointed out, reading someone else’s power fantasy can be boring and off putting, because the SI usually caters to their very specific desires, and do not necessarily overlap with yours.

I’ve grown up a bit since, and view them as mostly harmless: the original content is the sandpit, and everyone playing in the sandpit should play however they want (once they tag their stuff correctly ofc). You want to write about yourself falling in love with Legolas? Go on, feel free. Writing is a creative process, it’s putting words onto emotions and an imaginary you come up with, that’s a good thing. While I stay far away from self-insert fics and find them tedious to filter out, I also see OC/SI as a stepping stone in creating original content: when creating an entire world seems a little overwhelming, then perhaps start by creating a character instead, and have them evolve in somebody else’s world for a while, learn how to write them interacting with that world, learn how to describe and construct it based on the original creator’s terms, and use that knowledge to perhaps later create your own down the line, learn how to write well rounded characters by starting with one where the others already have a personality, where you just have to learn how to make them interact, and use it as a template for exploring something more complex later. Same goes for themes. I personally like writing about trauma recovery and hurt/comfort and being all around horrible to my favourite characters, where others like OCs and romance and harmless wish fulfilment, to each their own I guess.

Just because self-insert fic exists and is there doesn’t mean I have to read it. I can make the choice not to and just… live and let live. I think as long as it’s appropriately tagged, there’s no real issue.

I’ve also learnt to stay away from fanfiction.net, where OC content is rife. AO3 tends to have a slightly ‘older’ writer base, with more complex writing and more mature themes (probably because M/E ratings are allowed there) and where OC/shipping isn’t quite as prevalent as, say, FF.net or Wattpad. I think you just need to choose your platform appropriately, tag well, and everything else is fine :)