Why not remove the Attack Speed from Youmuu's Ghostblade?

I mean, Riot's gone so far as to state that:

Youmuu's Ghostblade fills this ‘core scaling item’ niche for casters and assassins, but also everyone who builds AD due to how much power it brings in raw stats.

And while a flat AD Nerf is a pretty universal nerf to all users of this item, I honestly think that if the goal is to pull it away from everyone that builds AD to just the niche of Casters and Assassins, taking away the Attack Speed would be a more definite way of solidifying its niche. If what Riot said is just the PR to hide that they want to nerf this item as a whole - and we can't blame them, we all should know by now this item is pretty over the top as is - then the general nerf is certainly justifiable. On the other hand though, you're shooting the Casters and the Assassins in the foot harder than, say, Auto Attackers in removing a Flat stat like AD over a % stat like Attack Speed. We already got rid of the Attack Speed from Maw for similar-ish reasons way back when; perhaps it's Youmuu's turn for the same treatment.