Remind me which series has consistently brought in glacial Japanese sales on consoles that weren't on death's doorstop?
Sakurai seemingly being oblivious about Ridley and Nintendo advertising the sequel to a game that had just finished selling more than the combined Metroid Prime trilogy are two completely different things.
They are both symptoms of Nintendo being out of touch with what fans
currently want.
Nintendo should know that Ridley was and is the most wanted and talked about potential Newcomer for Smash 4 by a good margin. Nintendo should also have known that just about 0% of the people who avidly follow video games were expecting or hoping for Retro's heavily secret game to be a DKCR sequel.
In the couple years leading up to Tropical Freeze's reveal you'd read so much hype online about how awesome Retro's secret project was going to be and how it was going to be the Wii U's quintessential graphical showcase. Most people thought it would be a beautiful new 3D Metroid, an epic StarFox reboot that would do for Star Fox what DKCR did for Donkey Kong, or an entirely new IP. A game like that could've been a great system seller. I'm sure you're aware of the crying (as your gifs point out) that happened when Tropical Freeze was revealed. The customers were not satisfied.
The desires of the vast majority of core Nintendo fans changed between the time Donkey Kong Country Returns came out and the time that Tropical Freeze was revealed. People were foaming at the mouth for Retro – one of Nintendo's best studios and known for their graphic prowess and ability to create 3D worlds – to make a new Star Fox, a new F-Zero, or a new Metroid after the tragedy of Other M. Nintendo was oblivious to the fact that most people wanted Retro to tackle a franchise they hadn't worked on before, or to save the Metroid franchise.
So I'd say Nintendo's obliviousness towards fans' overwhelming support for playable Ridley is a misreading of the majority desires of their customers. They see that people love Ridley and want him in Smash, but they may very well be missing the fact that everyone wants him to be
playable, and would be very disappointed if he were merely another boss, or, worse still, demoted to stage hazard.