In other words, you're saying he dies because the other team has knockups and enough punishment to kill him in 1 second, soley due to the skill level of the elo putting fights together and tight.
I've played Plat/Diamond, and I've played Silver/Gold, and here's what I find:
Yes. At high elo, players know how to collapse on someone immediately when an opportunistic cc hits them (just had a Diamond game this morning where I Jungled Leona vs a Xerath, Ashe, Zilean, Gangplank, Lee Sin. I spent the entire game pretty much just ulting Lee Sin and Ashe, and as soon as I did, even if I was out of timing, our mid Lux was just blowing up every stun, even though Lee was being a slippery devil. I couldn't get a lot of Q's in because Zilean and Xerath were Zoning my Leona with slow after slow along with Gangplank barrels, but that didn't stop my Lux from just destroying them).
I'm sure most of your Garen games also have an early game
, but in Mid/Low elos, a Mage just can't get Garen low enough to proc Grievous wounds, and no one really builds Execution there.
He also is tanky enough that if you ignore him, he has Demolish and pretty much 3 shots a turret, and most teams don't have consistent enough knockups. Since I do Zyra, I do occasionally have one Knockup, as with Nami, but those don't really seal the deal vs a Garen who always has a 