I don't agree with the Veigar changes, but the logic was, Veigar could zone out an entire team or split the enemy team with a very long stun.
Annie's stun has neither the duration nor the AOE of Veigar's stun.
Obviously Annie's stun is not the problem; people have a problem with her burst. The trick to beating Annie is realizing that her late game is shit if she doesn't get fed due to her weak mobility. She is an early/mid game snowballer with zero mobility, low range and relatively weak AOE. She can't win just by farming, she has to actively suppress the enemy carries from getting big. It isn't like Azir, Cass or Karthus who just have to AFK farm, and even if they are 0-10, once they get 4-5 slotted they'll melt the entire enemy team.
That means stop taking ignite against her, group early after taking a tower to deny her picks, and overall changing your strategy to win the game, rather than do the same thing that doesn't work over and over again.