So it is better for a champion that is annoying to be useless than actually viable. What if your main was suddenly thought of as toxic by the community? Would you like it if they were then gutted into unviability? Because any champion that annoys people should be gutted, correct?
Veigar does have low counter-play in the late game because of his instantaneous 2.5 second stun, and with how his ult instantly kills anyone with ap, I admit that. Veigar has a horrible early game however, and that is where he is held in check. In the early game anytime Veigar wants to stop hugging tower he either has to have his stun up, or risk being insta-killed since he is squishy, immobile, and the rest of his kit is just damage.
In my honest opinion, Veigar has a very healthy power curve over a match. He starts off very weak and is mostly a free kill for any assassin with a gap-closer pre-6. Yes he can get AP stacks from his Q, but that isn't very noticeable until late game. Veigar then gets his ult at the the start of the mid-game but is still very fragile, getting killed near instantly by anyone who isn't insta bursted. He then gets to late game where all of the punishment he got earlier can be paid back. His Q stacks become noticeable and his stun is game-changing. Veigar has a strong late-game because the rest of the game game is suffering once enemies realize how he easy he is to kill as long as his stun isn't up.