Pauline and Cappy don't have their chance yet. I already came up with an analogy being "the equivalent of Pauline having a spotty record of being playable" because that's Rosalina prior to her being playable. She got boosted from Mario Kart and Super Mario 3D World, but she's absent in a lot of the spinoffs including Mario Tennis Open, Mario & Sonic, Mario Super Sluggers, Mario Party 9, Super Smash Bros. Brawl (no if Corrin had the opportunity to be playable before his game was released, so can Rosalina). She may as well be absent in Mario Party: Island Tour.
I just tried to come up with why Rosalina might be favored over Toad, but I didn't mean to take it as indisputable fact as you did and disregard my disagreement with it. I'd still prefer Toad over Rosalina any time of the day.
And I think Toad was just unfortunate enough to be part of a side-special move by Peach, even though it's not like multiple Toads don't exist, and we also now have Captain Toad. I just feel Toad, the guy who's playable in the vast majority of Mario Kart, even back in Super Mario Kart, and playable in Super Mario Bros. 2 and 3D World as well as being a major presence in promotional material, received the short end of the stick.
And while I'd like to play another Mario (especially if potentially his voice won't sound like utter shit), I think Paper Mario sounds.... lame. Call me unimaginative, but I can't imagine Paper Mario being among the cast and I feel his contribution to the Mario series is better represented in stages and collectibles.