My unpopular opinion is that I don't really care for C-D characters from established Nintendo series being in Smash.
I always see people complain about the playable lineup for both Kirby and Zelda, but I've always been unfazed by it because there's no other characters in those series that feel essential outside of the main three.
I like that, for the most part, Smash just focuses on protagonists. The only exceptions thus far are clones (which don't take up much development time and add extra fanservice), or the actual importanting reoccuring characters like Peach, Bowser, K. Rool, Zelda, Ridley, Dedede, etc.
I just don't think characters like Ashley, Waluigi, Bandana Dee, any one-off Zelda character, Marx, etc are really on their level, and obviously they can't work as clones. At this point, I'd just prefer them to keep focusing on adding protagonists from currently unrepped series. Though I'd like Dixie.