Alright I don't know who said it, but its time for me to Weigh in.
Why do people think Bandanna dee is generic?
I'm gonna start with this overview of his moveset that shows the best usage:
mild spoilers for Star allies though:
First since I have to say, who else is using the spear? That's right no other candidate. It's not required for him to use a unique weapon but it helps him stand out and is part of his appeal.
Second, Bandanna dee has been around for a long time. He's used throwing stars, could use the beam easily, and his signature weapon the spear. Oh and let's not forget this:
The place it all began, megaton punch, where Dee was a rival and able to deliver a lightening fast karate chop, breaking stone pillars. Let's not also forget Kirby can hit a ****ing meteor with a baseball bat in this. Something they honestly could pull as Dee was in super star.
Also unlike Kirby, Bandanna Dee's bandanna is not the fighting one, so he could do this with his bare hands.
Easily that can be in his moveset.
Now moving on. Let's say the beam gets involved. That's an easy and kick ass aerial right now. He could backflip into the air launch a fully charged blast from the beam and be pretty scary to see.
Recovery? He's got something pretty sweet in that department. The spear Copter. Able to fly with it, he could plow through enemies too if they really wanted. Making Bandanna Dee having a scary moveset as any move could be completely different and would require a lot of tech.
Alright now to the main event how would his spears stand out? His standard attack with be the rapid fire of the spears working like Marth's dancing blade but able to launch Dee forward. If Sakurai really wanted he could also have a dash based on the katanna strike from Kirby. Yes that's a different powerup but it wouldn't be a stretch for a spear to work similarly.
As you can see in the video there's also the triple spear launch. Being able to control its angle and spread would be pretty big with competitive play imo. And I imagine bandanna dee being one of the fastest characters making his moves flashy and quick.
Final Smash?
As the commander of Dedede's Army he summons the rest of the troops as they launch a barrage of attacks. Dee then comes in with the finisher, the aforementioned MEGATON PUNCH!
With a moveset capability, the tech he could have, the speed he would play, and his role in Kirby games, can you really say Dee would be generic? He's far from it and would easily appeal to people with a flashy trailer showing off such a diverse and powerful moveset as well as gaining fans of his hyped and peaking the interest of others.
But that's my take. I never got the goomba with a hat philosophy. Its so flawed and makes it sound like a person has never played Kirby before. People just need to look at the history and Sakurai, and they'll know he can do some amazing things with such a fantastic character.