How do you learn a new champ without getting wrecked?

Bots might teach you the buttons, but the mode doesn't even come close to simulating an actual human and pretty much lets you win. even intermediates only punish you for diving 1v5 with perfectly chained CC, wehich I already know not to do.

I'm mid-high silver with the champs I know and those that are similar, but wood tier with most assassins, toplaners of any flavor, and not all that much better on ADCs. Normals typically pair me with golds and plats with a smattering of silvers, and the occasional bronze if he's queued with like a diamond, so I get people already above my real level with champs and playstyles I don't know, and they're typically playing a favorite. How does one deal with it and learn?