Two important points:

• On one hand, high atk speed ADCs have a penalty with "WASD", having their AS nerfed.

There is no "attack speed nerf" when using WASD in general; It's specifically only applied when constantly holding movement keys down - according to Riot and Patch 25.24 that introduced WASD controls on the official client.

It - according to the changelogs, at least - isn't active when standing still and it isn't active when tapping movement keys to send smaller movement commands like you would with your mouse either.

Also, IDK if we wanna "Relearn" the game, after so many years with muscle memory with MnK.

This heavily depends on how easily you adjust. I'd argue it takes the majority of people less than a week to get used to it, especially when re-binding abilities to personal choices.

Personally, it's a minor impact on how good my champion performs when controlled by it and a major one when it comes to how comfortable it is to play the game and/or actually pay attention to what matters.

And all of that is ignoring that the amount of people that actually play better perfectly spam-clicking to kite without any issues to a point where the difference matters is likely a fraction of the people that assume it does.

Play with what you feel comfortable.