Here's the thing:
Most high elos are seeded, and have been since about Season 5. They gain a baseline provisional score higher than anyone else, and easily maintain their 5%+ of the community status.
The game is invariably easier for them to accomplish Challenger/Masters than anyone else to. What changes is generally simply the order or ranking in that 5% or less.
Skill does matter when you're comparing a Sub-Gold to people above gold. But..... it's generally knowledge to abuse some reset assassin, or hard counter mechanics. It's not always "Skill."
Yesterday, I had the pleasure to have a Diamond + Zed in a Silver game. I as Nami got a Jinx to rage quit vs me and a Vayne - literally every time she got back to lane she was instant dead. She wasn't even playing bad - She just ..... got hit by accurate bubbles, while E slow did the rest. She didn't even have room to "play safe."
Didn't matter that we hard stomped the game. The Zed was better. We were fed beyond belief, but this Zed..... had 0 counterplay, simply because Nami skills have delays, she's squishy even when she embarks on a nonsquishy path, and because Zed began purposefully hunting me.
Without me, the Vayne couldn't do much either. Her play requires her to actually have time to go through 4-5 volleys of attacks, while Zed only has to hit everything in .5 seconds. So they'd dance awhile, and Vayne would actually be mechanically playing better than Zed, get in 3-4 hits, but somewhere during her Ult, when she popped out of invisibility, Zed would just annihilate her.
I think we actually won the game, because Zed's team surrendered the 4v5, but if they didn't realistically, Zed purely controlled the game simply because there was no counterplay to a good Zed.
Skill matters some. What champ you express that skill through matters more. And where you are pre-seeded matters most.