well, counterplay does exist for them, that's all i'm saying. And I'm saying that because I'm assuming you're what, low gold? If you figure out how to beat a champion at their own game, then you get better. Examples:
Hard CC and Burst isnt the answer to everything, but vayne is low range and squishy as hell. shes the anti tank though. I can beat a fed caitlyn as an unfed nautilus, that's what i'm saying. Also, vayne has a shite early game. If you watch streamers or high elo players sometimes they surrender aftr a certain point because the enemy has outscaled them. That's also a part of the game. Some champs become huge in the late, and then its harder for one team comp to execute a game-winning fight than another. An argument for that is assassins. Assassins are pick-off champs, not teamfighters. In the late game teams tend to group up for objectives. Assassins wont be as relevant then. However, vayne can always be picked off. My favorite into her is Bruiser wukong. can't qss knockups.
Warding deep allows you to predict where he's coming from. you see him bot, you lean top. If you can't fight him, then don't. Hecarim is strong early, so yes, ward deep. doesn't even have to be super deep. in the midlane, my favorite ward is in the river opening by the raptors and red buff. Just in that pass you can see him go to raptors, red, and you can spot him in the river. when you do, move away. If you cannot win the fight, then don't fight him. It's that simple.
Lee sin is SO easy to counter. In lane before he has kick, just ward nearby to spot him ganking. When he does, stay in the middle of the lane rather than leaning to an edge. That's how he connects easier with you. otherwise he wastes a ward and an escape to get to you, allowing you to fight him or get a 1 for 1 if he's greedy. If he has kick, this principle applies even more so. Lee is hella beatable, because most often they tend to outplay themselves.
And you're exactly right. Thinking is the solution to everything. You have to play smart. If they're unfun to play against, ban them. otherwise, if they're meta, learn to play against them. also, all the champs you mentioned are early game dominators (except vayne who's known as THE lategame monster). Heca, lee, cait, janna, Vi... they're early game champs. Cait has a midgame power drop, janna is squishy, vi has a mediocre at best late game, lee becomes harder to play well later... If you know how to abuse this, you'll win. The fact that you can't or are not willing to recognize a champ's strengths and weaknesses shows you don't think enough, and you won't climb that way. I agree some champs need nerfs, but they're not unbeatable. Not one champ is.