How do I win when my team completely ignores me?

So enemy team almost aced us and got baron buff, we respawned and I (adc) saw Malphite coming to take our open inhibitor. I asked for someone to come help me as I wasn't a vayne and he could probably just burst me down (he had went full armour and thornmail), instead the team decided to engage a 4v4 fight without me and all died, killing one person. I don't get how I'm meant to climb when people do stuff like this.
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