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IVs are the worst mechanic in the game.
They're the main reason that breeding is such a hassle. Gamefreak has been drip-feeding us features (ways to influence IVs/Natures, Bottle Caps, Raid Pokemon having guaranteed 1-4 perfect IVs, etc.) to make them less agonizing rather than just biting the bullet and ridding of them entirely.
Gamefreak says they're for flavor purposes and to give each player a unique experience, as in all creatures are different and have varying levels of ability just like in real life, but realism does not always make for a fun or enticing game mechanic. It's especially backwards considering IVs might encourage players to play a game of eugenics and selective breeding, actively going against Gamefreak's design to not only have a streamlined entry-level RPG, but also going against their claim that "Pokemon aren't battle machines, they are our friends, uwu".
IVs do nothing for the game other than create an unnecessary bridge between casual and competitive and add almost no complexity towards the latter considering the number of valid IV spreads can be counted on a single hand with very few exceptions.
The games would be better if IVs were removed entirely and the games were balanced around that instead. While we're at it, make it so that EVs aren't applied automatically when earned and you have to allocate them manually. Natures are fine I guess, but they still need work too.