Assassin mains want you to believe they require skill so they can tell you how awesome they are when they get 20 kills in a game by pressing two buttons.
Example:
Talon.
Starts off the lane, gets level 2 (especially if you are still level one) by hard-pushing with W. Immediately raises Q, flashes to you, ignite, auto-Q-auto, doing this immediately after just barely nicking you with the "skill shot" of W that is impossible to miss.
Many times he can kill you without even landing a whole combo. Such as if you flash away when he flashes, he can Q to you and still kill you many times. Definitely if you are still level 1.
Very, very few champions can live through this all-in and certainly no squishy targets.
So... you say there is counter-play to this?
Just stay back and do not let him eh?
Well.. problem is, he then controls the wave. Easily zoning you back from experience and CS as the wave starts towards you, he lands W on you at will. When you are equal level to him, he is now up in health. If you push out at all, he kills you on the spot.
And so, say you are playing a mage against him... he has the highest MR of anyone in the game, added on his defense rune of MR, making him take significantly less damage from you, while having all-in potential at level 2 (sometimes even level one if you mess up), taking less poke damage than you take from his W and he has total control over the way the game is played.
Now... you may try to say a mage has range... But I already pointed out the difference in MR but to further drive this home, almost all mages armor is really low at base. Add to that the armor rune for defense is 2 points lower than the MR rune.
So, not only is he tougher than you, has better poke than you, but he even has more sustain (higher base health regen). In fact, his typical starting item of a long sword give him an advantage in getting his required items earlier.
But let us really break this down. Say you actually turtle, giving up experience and gold to a talon player (which is what he needs, to be ahead). He then finishes his tiamat and mobility boots (because he is too powerful to really care about needing real boots)... And guess what happens? Your teammates become the gold source for him.
Especially once he gets Duskblade and vision is literally meaningless at that point.
The entire game becomes an attempt to not feed this person that can easily all-in kill almost anyone in the game with almost no skill required.
My very first game playing this fellow I got first blood in the game by just doing the above combo. I then killed the enemy laner almost immediately when they returned to the game and then killed the JG that showed up right with them. The game was over at that point.
His snowball is such that you lose once he is ahead, even with inexperience.
Becoming invisible, diving over walls with nigh-infinite dashes and automatically deleting almost any target gives no chance for interaction.
Which is, fundamentally, the core of almost every assassin.
Half the AP assassins are actually somewhat interactive. Fizz, Ekko, etc all have pretty clear times to punish.
Akali? Hahahahahahahaahahahahahahahahahahahahahahaha (just watch any pro game or high elo player)
LeBlanc? Ummm...??
Talon? Millions of dashes, invisibility, tons of movement and insta-burst damage...
Qiyana? Ranged CC, dashes, AoE Stuns and knockbacks... Yep.. Interactive... --
Ahri? Hahahahahahaha.... Has three dashes, plus flash, ranged CC, true damage, AoE wave clear, healing.. Probably the single safest champion ever built with tons of damage and, as mentioned, CC????
Katarina? Yeah.. Super interactive there. Dash, kill, dash, kill, dash, AoE kill team, dash....
Pyke? Need I say more? The most uninteractive champion ever, including Yuumi
Kayn? I mean... he walks through walls and literally becomes untargetable to kill someone from the inside... Also has multiple CCs and healing.... --
And I can continue...
I have made posts about this before but the usual assassin mains and Riot White-Knights will come swooping in from the heavens to tell you that they are high-skilled champions with impossible mechanics... Except you can pick them up in a handful of games (with like two-three exceptions).