I can only guess that at the previous Nintendo Direct, even Sakurai wasn't sure if Ridley would be playable. It looks like the team tried—they chose the Other M version to make his aspect ratio work better when scaled, crafted a Meta Ridley final smash, gave him his own icon, animated him to walk on the ground, grab edges, explode when knocked offscreen... but ultimately, they didn't think he worked well for some reason. And so, instead of losing that work, they converted him into a mixture of a stage boss and an ally.
I think there are too many parallels with playable characters to deny that they tried, and I am grateful for that and not in the least angry or embittered. Ridley's been my #1 desired playable character since anticipating Brawl, and at this point, seeing this, I admit to being disheartened at the possibility that he will ever be playable. It really does look like they made a very noble effort. (Thanks to all of the devs that worked on this—I'm sure this was hard for you, too. Much appreciation.)
It will be a very interesting discussion at the next Smash Bros Roundtable, I'm sure.
And I would still buy a Ridley Amiibo. Especially if he can be playable in Mario Kart.