The thing about the Koopalings is, usually, if you get one, you get all seven, which is a big chunk of whatever roster that could be dedicated to branching out in other ways. Smash did it right, by making them all alts of the same character. Their appearance on the MK roster, for example, comes off a little like filler, especially when they consistently choose to omit unique characters like E. Gadd, Kamek, almost anyone from DKC, or even past ones like Petey Piranha and Birdo.
Well, they're part of why it feels like filler, the other is the increasing amount of derivative characters like Mario and Peach covered in various alloys or a completely unnecessary amount of baby characters (that don't even use existing ones like Baby Wario or Baby DK).
I really don't get it. The Mario series has such better options to work with. I don't even bother entertaining the possibility of RPG characters getting acknowledged, because that seems like a total lost cause (outside of Smash, at least). But it does make me happy that EPD doesn't create, or really seem to influence the Smash roster at all. Three Links would actually look tame in comparison to their version.
But **** would Geno and Mallow have fit right in to Double Dash perfectly.
I think they do it on purpose, because Mario has to be casual, and fanservice has to stay at a minimum.
Think of a kid who has never played a Mario game: that kid must be able to understand all the content of any Mario game even with 0 experience with the series.
This is why when an old character is reintroduced, it's treated as if it was a new character, with little focus on their past roles (think of Pauline, or even Daisy at the time when she came back from Marioland), and when there's an actual reference to an older more obscure game element, it's extremely minor or left ambiguous (Sherbet Land in Mario Kart is probably a reference to the same location from Warioland, but it's still not clear if it's intentional or just a coincidence, because there is no Warioland element in the tracks with that name).
Baby characters are cute, who cares if they aren't canon? Baby DK is canon? That character from Yoshi's Island DS? You have to ask many questions and do research in order to fully understand it, so it's not worth, because you know, Baby Rosalina is cuter than Baby DK, so why spend effort in making a baby monkey? Not to mention Baby Wario. (I'm sarcastic obviously).
Mario must not have a real continuity, it must not have an hardcore community that can potentially create discrimination among fans; new game, new world... everything back from start, every player comes back to being a casual because their prior knownledge becomes useless, events from previous games won't be referenced aside of some very minor easter eggs.
When a character is excluded (such as Waluigi in MK7) it's probably because it doesn't fit the specific mood of that particular version of the game, or because they already have another character who appeals to the same type of players the removed character was appealing to, and its presence would be unnecessary; or even worse, maybe so in the future they can release another similar game with the missing character included, so that the new game feels different. they do this type of character rotation in some games, especially in Mario Party.
I literally stopped being a Mario fanboy when I realized they were treating the franchise this way, and it happend around Mario Galaxy/Mario Kart Wii.
I'm honestly surprised that Funky Kong in MKWii was a thing actually, because it's the only character who don't fit the logic; it must have been a favorite of the developers or something. Oh, and ROB... WTF they were thinking/planning when they put ROB in MKDS?