"champion winrates don't matter in lower ranks"
We need to stop with this mindset. Most of the time champion winrates stay the same throughout all elos. You can say "if you play well it doesn't matter" If the enemy team stacks high winrate champions (53+) and yours don't and sometimes picks low winrate champs, your win chance can get below 30%. This does not take into account champion matchups, and in some cases, it can get as low as 20% before the game even starts.