The outcry for Toad might not be as piercing as Ridley's was, but it's still definitely there and grows every game. If fan demand could push an unfeasible character over the edge, then I don't see why fan demand can't push a kind of boring character over the edge.
I don't fault you for thinking this way, but I do have my doubts as to whether Toad's more moderate support is enough to serve him very well here.
In my perspective these kind of characters fall into two categories that can be overcome. One is the fan demand category, the other is the status-quo. Again though, this is MY perspective and founded in what we've seen so far. It doesn't mean that characters can't bend the rules, or only fall loosely into these categories, but for me its a safe way to justify more "unrealistic" choices whether it's word of god or just an unfortunate pattern that has given us that idea.
Ridley is a fan demand pick. The constant, unflinching pressure from the community to reconsider his stance inevitably put Ridley in the front of Sakurai's mind since Brawl. And after being pressured to think about the character for three games in a row, he finally came up with a solution. Toad has support, but not at this level. He is a popular character in the mainstream, obviously, but his presence is an unobtrusive and passive one within Smash discussions. If he was added to Smash, I don't think it would be his continued demand that would do it, there is not very much external pressure guiding Sakurai's mind.
Villager is a status quo pick... or rather, a choice in response to a
changing status quo. Once upon a time Villager was deemed a poor choice for a playable character, but Animal Crossing's continued success (and perhaps some nudging from Nintendo?) led Sakurai to give it another go. It only took a couple Smash games to get there, and as of Brawl the series only had two entries anyway. By Smash 4, that was up to four installments. Seeing Animal Crossing become a more prominent fixture in Nintendo's arsenal, it became harder and harder to justify ignoring it. On the contrary, outside of the aforementioned Captain Toad bump we just discussed, Toad's role in the series has remained pretty consistent. Is there enough going on right now to reassess?
Honestly, it's possible that there is. Toad's presence within the Mario brand is so omnipresent that it became a criticism for several years. He has a notable presence at the theme parks (mascot suit, wristband), he had a prominent role in a billion dollar grossing feature film. So I think this latter point, these status-quo changes where Toad is further pushed into the spotlight via both standard Mario titles and multimedia expansion are the ones you want to hedge on the most when making a case for him. I guess a lot of this has more to do with Mario's brand expansion as a whole, but it speaks to something relevant that Toad has been present for all of it.
My stance on Toad is very much that I'll believe it when I see it, but the strongest argument in his favor (or pretty much any character's favor, really) is acknowledging how much has changed for them between then and now. Whether that's the progression of a series or a community movement.