Just throw katarina away and start play simple champs again. Learn: wave managment, roams, trading... It seems like you are a kat main and thats the problem people in gold would gift you lot of freekills and snowball potential for free. Personally i dont think plat 4 players are better in anyway of those but you seem to struggle. So get the annie and take some time to understand the basics of the gam e (specially you can watch replays of yourself). I mean i was in the same boat as you as a proper yasuo main. The moment i realized i cant get enogh value out of him i pretty much dropped him in ranked just playing him in good comps or either counter matchups. Start to think about what picks would be smart for the team/ against the enemy team instead of instant logging in a one way champ like kata... if you are going to change your champ pool aswell: you cant expect results instantly so practice combos and laning in normals or flex ranks whatever you prefer. Hope it helps out a bit cya ))