You don't win every game regardless of your role, support isn't unique in that way.
As a solo queue support main, the key tends to be figuring out who the best player on your team is, and who the worst is. Either get the former super fed and/or keep them alive, or babysit the worst one so you can keep them from feeding too much until the rest of the team can get by. Which one you focus on would vary based on your support choice and the particular skill levels of those involved and/or their scalings.
I actually kinda like climbing as a solo support main, because I'm confident in my own play so I expect to be able to outplay my opponents, but by the nature of support (...when played properly) you 'force' someone else to become really strong too, and then it becomes two people carrying the game, instead of other roles where if you're a god, you're still just one person.