Why are people complaining about kassadin?

an auto with a w auto reset tends to hurt alot with thunder lords

I honestly do not know why.

Crikey! I main Kassadin and have Level 7 Mastery on him, and I can attest that his laning phase is shitty until he hits level 6. Speaking from personal experience, I think the reason people are salty about Kassadin is that he currently counters most of the META mid laners. He might need a baby-sized nerf (like maybe a slight increase in the mana cost on his E), but I think he's fine for the most part. If people want to complain about champions who are truly broken, then they should focus on Zac or Fizz instead. Gooday to you, mate.

The few times I've laned against Kass recently, it seems to me that he has VERY good poke. His single-target damage skill has decent range and gives him a magic shield that stops people from trading with him favorably. That alone makes him kinda hard to deal with for me (I was playing Swain).

If I ever did go to combo him, the magic shield + minion aggro made me take as much damage as I gave, and he could keep harassing me on top of that. Not a fun time.

He can't be THAT oppressive, or he'd have better stats. Maybe Swain is just a good matchup for him?

The issue is not that he gives you a hard time in lane, but more that it's not that easy to give him a hard time while his post 6 gets rather powerfull with absurd roaming potential.