While I do think Sakurai is oblivious sometimes, I don't think he is in regards to Ridley. There's just no way anyone can misinterpret the enormous and all devouring subject that is Ridley, he dominates the majority of character discussions for each game, and Sakurai has likely heard the complaints about Ridley's role in Brawl too. Heck, I'm certain he knew about the demand for a playable Ridley for Brawl too, he just chose to not deliver back then, which was no big deal since he gave us almost every other highly requested character anyways, Sonic included.
You can say many things about Sakurai and his decisions, you can give him all the hate in the world over tripping itself or w/e, but if there's one thing even I can see, it's that he understands the fanbase's character requests. The way he interacted with us through the Direct, the way he teased Palutena and Ridley, Sakurai knows how to communicate with us, he speaks our language, it's very obvious. There's no way he has simply misinterpreted that we want Ridley as a playable character and not a boss.
Anyways, I'm off to bed now.