Yeah, maybe they've held back with characters people wanted for DLC in order to get more sales. Sneaky, but it'll probably work if they put Diddy, Bowser Jr and Birdo(to a lesser extent) in a pack since the three are pretty popular. Maybe we'll get Petey, King Boo or Nabbit too.
Baby Rosalina was added because they're shoe horning her in everywhere they can at the moment. Kind of like when they shoved Petey in everything. Only difference is she'll probably be around for a while and not fade out of spinoffs like he did.
Yoshi's also popular, and my favourite character of all time, but ffs do not add Baby Yoshi into the next Mario Kart Nintendo. Or Baby Toad. I'll let Baby Wario and DK slide since they're big parts of Yoshi's Island DS like Baby Peach was.
To be fair I think it's really unfair to shun character additions people want in order to add OCs that are just remodelled versions of other characters.
I'm not alone in this judging by the general reaction to Baby Rosalina and Pink Gold Peach.
As you said though maybe a DLC pack will fix this up anyway. Guess we'll have to wait and see.
They're not shoe horning her. Shoe horning is when you put them in places they don't make sense. But why shouldn't Rosalina be included in Mario games that are a celebration of the franchise, when she is a main character? Honestly, I feel at this point, people are just looking for someone to point the finger at when certain characters don't make the cut in Mario Kart and Smash, and Rosalina has been the unlucky choice for some reason. People go on about how she has "been in everything", but she's only been in 10 games (including the ones that have yet to be released, but we know she is in). 3 main series games, 4 Mario Kart games, and 3 other games (including Smash). In three of these appearances, she is not playable. The amount of games Rosalina has been in at least fits on my computer screen very easily. And she has skipped out on plenty of games since her debut, including 3 Mario Party games (and even in the one she is in, she is not playable), 3D Land, various sports games (one of which she was supposed to be in, but was cut from), the Mario & Sonic games, and more. Yet, Birdo's appearances can't even fit on my monitor screen. Same will be said about many other characters people are getting worked up about.
Also, Baby Yoshis actually canonically exist in plenty of games, I don't see how they are an unjustified addition. Heck, Baby Yoshi debuted with Yoshi in Super Mario World.
And I'm not shunning characters people like. I have no problem with any Mario Kart characters besides Metal Mario and Pink Gold Peach. I don't care about Daisy at all (and find her very overrated and kind of annoying), for example, yet I've always been OK with Baby Daisy. I just don't like how people are pinning the blame on Rosalina when there is no precedence to blame the absence of other characters from various games on her. Some characters get in. Some don't. That's just how it is. It's no reason to start getting angry at certain characters for no reason, or to not buy the game over.
And let's pretend Diddy, Bowser.Jr, etc, aren't in this game at all, and that they definitely won't be DLC - won't that make their inevitable return to the series all the more exciting in the next game?