That's part of what bugs me too. People will crap all over the idea of Toad, Bowser Jr., Waluigi, and Daisy despite the fact that they're really not all that different from Rosalina in the grand scheme of Mario. People still argue that none of these characters have any real potential but did anyone seriously imagine Rosalina as a puppet user? Come on...
Look, your being mad over Rosalina is really showing pretty hard. You really need to just let it go. No one here is going to give you the answer you want.
Also, not only are those people you listed nothing like Rosalina, but they're nothing like
each other either.
Toad is his own case, Bowser Jr. is his own (despite really having no place in the Mario series as a whole other than being Bowser's Scrappy Doo), Daisy has needed more recognition for a long time since she's her own individual character and did start out in the main series and Waluigi...Well, he's Waluigi. He's a special case in his own right. He's honestly just very entertaining and fun to watch and would be equally fun to play. Not needed, but wouldn't hurt to have. But even then, none of them compare to how much depth and interest Rosalina gave when she appeared and since then.
In my eyes, Rosalina is akin to Blaze the Cat from the Sonic series. A character comprised of similar elements to one or two past characters but is better fleshed out and well-rounded to the point of drawing not only a lot more interest from others, but great deal of respect and a general desire to see them again if there were to be other characters. They start off being mildly popular though some or most may not know them, then end up being immensely popular to the point that the majority wants more of them at any cost. They often end up being considered the best new character to be made from the franchise in years even if they don't show up in a lot of things. There's a lot of potential in them and if the company in charge sees it, they're going to put them out there for them to shine at any possible time. (Though that part applies more for Rosalina right now since the Sonic series is still suffering from Solo-Sonica Disease.)
And to that last question did many imagine her as a puppet user? Some actually did, but not a lot. But
can we see her as one due to her backstory, concept and place in the series? Hell yeah. It's all kinds of believable, makes perfect sense and only adds to her interesting nature and her attractiveness.
That said, in the grand scheme of things, there's no point in talking about Mario characters because we can all agree that we've had enough of them. Pokemon, Zelda and Metroid really need something. Maybe even Kid Icarus or Fire Emblem. Donkey Kong too. Anyone else.