Ashe is extremely vulnerable to any kind of gapcloser, her slow is ultimately entirely useless against those, and you can stack 70%+ tenacity if you actually want to.
That means her passive damage boost gets outright disabled if she doesn't attack you twice each second......
Kog play the range game? He relies entirely on someone stunning and slowing the diver for him, if they get ontop of him he can't do anything by himself.
And actually the movespeed tends to be around 430, which is still among the slower ones, have you ever seen how quickly anyone with predator goes? Marksmen without mobility rely on movespeed to avoid enemies but some things are just too fast to dodge x)
Kai sa? At max rank she gains a 150% movespeed buff.....for a entire 0,7 seconds..... Her kiting is worse than even Ashe.
And seriously? Are you even playing this game? Varus Q damage? Have you actually played under the last 10 months? This thing gets used for its damage in lane and never after, post that it's a tool to proc his W and nothing more, he wont have the AD to deal any kind of notable damage with it.
His Root is 2 seconds, with 60% tenacity which any melee can get if they want, that root will last for 0,8 seconds.....about as long as quinn E?
Draven relies on catching his Q to do any real damage so hes the damn most predicable marksman ever made, you can always tell where he is going and breaking his pattern is easy, only time he gets good is when he can aggressively trade, heal back up and go in again before the opponent can do the same, that or when he can deal a significantly higher amount of damage and gain a crushing lead from the start.
Sivir......literally one of the least played marksmen ever made because she dies too much regardless of how well you play? Spellshield? How about i wait for a second or just use some filler like ability for 1 second while she tries but fails to kill anything due to a lack of damage.
Her ulti is the only notable thing about her aside from waveclear, and if she uses it to run away then you can just back off and engage on her 30 seconds later and she´ll be boned, A spellshield does not have that much impact in the current game.
MF can indeed kite........the same things as Ashe, meaning slow and immobile melee, anything else and she dies pretty quickly, which is why she lets her support engage and stunlock targets while she ults them......which has gotten nerfed to the point where she is hardly played much either-
Xayah is indeed quite good at kiting melee, but you know....her root is extremely telegraphed, her speedup is pretty low and it's main use is a damage steroid, what really shines on her when it comes to surviving is her ulti, it lets you avoid big hits like Vi ulti, MF ulti or Ashe ulti.
She is very helpless without it though.
Have you actually played these champions? You make it sound like each and everyone of them is some impossible to catch animal that also cant be killed.......somehow i get the impression you´ve been playing against some extremely fed ones, a lot.
Smurf trauma?