Don't waste your time trying to get a lane even only apply pressure where you gain advantage it sucks that helping someone who is losing doesn't actually put them in a position to gain any advantages so just don't waste your time you gotta apply your pressure where it will give you the largest chance of winning.
Imagine an ally Gnar that is 0/3/0 vs a 3/0/1 Darius if you choose to apply your advantage to that lane the best off of 1 play you will get a 1/3/0 Gnar or a 0/3/1 Gnar both are still leagues behind the Darius so without your constant pressure there he will still keep losing. I know it doesn't sound ideal to play with this way but the wisest words I have heard from my diamond friend is "Don't gank for losing lanes."
This is a hard thing for most league players, but league is a team game if you want to win you need to do what you think is best for the team. That means applying your time and effort where it will have the best chance of winning the game. A lot of the time that means you need to set up a player to carry you. Example: Botlane is feeding but you have a Zed on your team. Get Zed fed if you are going to win it is probably because the assassin takes all the resources being funneled into the enemy ADC. Set him up to carry you apply your skill to make it easier for other members of your team to help you in the long run.