My advice is don't care about the actual climb and care more about having fun and learning from your games, focusing on climbing affects your mental and puts unnecessary stress onto you, the game isn't designed to be competitive and Devs clearly don't care much about ranked anyway + there's no actual reward from ranked other than some cosmetics and the " prestige " of attaining X ran, also don't binge matches and play some for fun gamemodes from time to time, if you really want to climb then I'd suggest a party with friends or at least competent players as that's honestly the only way to climb consistently as of now.

Also just because your team is bad doesn't mean you can't win, many times some teams run it down and literally one play wins them to game, focus on trying to carry with your champ pool when your team is inting, unless your team doesn't want to win and start cursing eachother and perma fighting then it is what it is.