I feel like I need to relearn this game

I’m lvl 420 but have been hard stuck between gold and plat for months now. I’ve come to the realisation that I’m just flat out shit. I lose lanes and games that I should win. How can I “relearn” the game. I would play draft but I feel like it sucks for getting better in ranked. How does a player as high level as me and with so much playtime improve anymore? It’s lowk making me a bit depressed having so much experience but nothing to show for it.