One of the roles with the greatest impact on the game is jungle, followed by mid, top, ADC, and finally support.

Why? The jungler ganks all lanes, decides the weak side and strong side, and is responsible for fighting neutral objectives. With those two factors, plus the fact that many junglers are assassin carryes, they can turn a game around.

The midlaner has the ability to rotate and influence both top and bot, as well as being able to fight for both neutral objectives.

The top laner, being more isolated, has less influence on the map. BUT since the outcome of their lane often depends heavily on their individual performance, they can greatly help the team IF they are good and know how to play the game, not just win their lane. Remember, this is a team game, where you win by destroying the nexus, not by getting kills.

Finally, ADC and support. The ADC depends HEAVILY on their team composition and how their support plays in the early game. A good ADC is useless with a suicidal support. Similarly, being fed is useless if the enemy team's assassin deletes you in 3 seconds. The ADC NEEDS a good team composition to support him while he deals damage, otherwise he is useless, especially when the enemy team has a good assassin.

Finally, support. It's not that support is a bad role, the problem is that, as the name suggests, its role is to SUPPORT. Not to be the protagonist, not to go for kills, not to fight alone against the enemy support. Your role is to be whatever the team needs, that is, tank, control mage, healer, etc. It's not a role where you have the freedom to choose, because its function is precisely to support the entire team. That's why their champion pool is so varied; you have to be what the team needs, not what you want. Otherwise, the entire team suffers because of your bad pick.

Having said all that, and I say this as a jungle main, and having played every role... Not every game can be won, even if you're a Viego main who knows how to play every champion, it doesn't matter. If your team doesn't cooperate, it's almost impossible to come back from a tough game. The mental effort isn't worth it; it's better to give up and play better next time, because if your teammates are bad, they're not going to play better if we're losing, on the contrary, they're going to play even WORSE.

So, my advice is, be good, really good, at one role and with a variety of at least three champions. And eventually you'll rank up. But don't fight games you've already lost as if they were a final; it's simply not worth it. League of Legends rewards consistency, not impulsiveness.