And yet your experience doesn't line up with mine in the slightest. I don't get feeding Katarinas on my team, even when she was a popular pick. Maybe that's because I'm a support person, so I'm always ready to peel for the carries regardless of what champion I play.
You can check Champion.gg. Katarina's winrate by games played as her shoots up quite quickly once you have 125+ games under your belt. In fact, it's only slightly worse than Azir's winrate at 125+ games. He's got a high skill ceiling, and he's also shit with little experience. Katarina seems to have a similar skill curve though not as drastic. While a lot of champions behave like this, most have a variance of about 3-4%, whereas she has almost 10% (and Azir almost 20%).
Telling me you have 5k games is actually suggesting to me more than you are simply biased to your own playstyle, not that you know most of everything about how to play her. I was in the same boat with Pantheon, as I would always swear by offtank/full-tank Pantheon instead of assassin.
I don't know what to tell you about to improve that though. She has above expected pick rate mid (~3%) and significantly high winrate when you have tons of experience (~53%). Champion.gg doesn't cross-reference variables, so I'm not sure what you could look for to change your game.
If you're as experienced with her as you say you are, then you should be able to pull a Descartes: scrap everything and rebuild your playstyle from the ground up based on iterative, empirical evidence of what works and what doesn't.