At what elo are teammates useful?

Everyone knows that silver and bronze are full of useless people. I've played games in gold and plat with equally useless people. I've watched streams of challenger players with useless diamonds, masters, and challengers.

At all elos do you just assume you're 1v9?

Let me give you an example:

You're blue jungler. Your team has priority mid and bot. You go for bot scuttle and the enemy jungler shows up. You know you can't out duel him, but you ping and expect your teammates will know to rotate since they have priority.

How do you know if you should go in? Should you just assume your bot and mid have absolutely no game knowledge and never make a risky play?

There are a lot of really good plays that can be made on this game that require you to assume your teammates have a brain. Can you just not make those plays until you're at the top of the challenger ladder?

This isn't to say that I never have teammates who are useful. As a mid main I ALWAYS back up my jungle unless I absolutely can't. This means that jungle and I often carry the game. When I jungle I never get the same courtesy unless my mid lane happens to be high plat+.

Anyway, what are your thoughts? How risky of plays are you willing to make with 4 random people on your team in your elo? I'd like to hear from people of all ranks.