Thinking about the echo newcomers for Ultimate, I think it was some of the Melee clone choices (and Ganondorf ending up a clone) that gave clones their bad reputation among the Smash Bros. community to begin with.
I actually wrote this nearly ten years ago (back in January 2009), so its weird to see some of it come true (ten years later), but a lot of it very wrong (Smash 4 was able to add in many unique newcomers while able to keep most of Brawl's roster).
However, despite there being more of an effort this time to make the clones more unique, many Smash Bros. fans still complained about them. Many people don’t realize that clones are actually a blessing. Clones help to boost up the roster (especially when development time is limited), increase the chances and allow for less likely characters to get in over more important ones (like how Dr. Mario was able to get in before Wario). A character such as Vaati would never be seriously considered (assuming he does not get any more games) for a newcomer list that only consisted of non-clone characters due to him not being important enough to warrant the development time needed to make a unique character. However, he would be one of the top contenders if Sakurai’s team went “clone crazy” as he would be an easy Zelda clone (really he would only need to have the magic changed to wind and dark magic, as well as have a new down-b and Final Smash).
Clones are especially important now more than ever. Sakurai’s struggled to get to 39 characters in Brawl, and since it is likely that Nintendo’s next console will have a sizable leap in graphical and technological prowess over the Wii (it should be about on par with the 360 or PS3), then Sakurai’s team will have an even more difficult time implementing a sizable increase for the roster. Assuming no characters from Brawl are cut, I can only see ten newcomers for this possible situation. However, many people make up the Smash Bros. fanbase would be hungry for more characters, and would “rage” to find out that Smash 4 only have 10 new characters.
That is where clones come in. Making five clones takes the effort of making one character (or at least that was what Sakurai implied back with Melee). Putting in five clones would boost the roster up to 50. However, I can see many people objecting to this. However, I think one of the main reasons people object to clones, if that in Melee, some of them (in their eyes) were poor choices. If I were to select 5 clones for Smash Bros. 4, I would try to select characters that were popularly requested and important to their respective series.
The example written about Vaati was poignant because it actually ended up happening with another villain who never appeared again in their own franchise (Dark Samus). Vaati being part of the Zelda series was just another face in the crowd unfortunately, while Dark Samus was still the most significant Metroid character after Ridley (especially if you did not ignore the Prime trilogy).
I also find it amusing ten years later for an upcoming Smash Bros. game we got FIVE newcomers that consisted of the cloniest type of clones ever, yet they were all well received for the most part.