I'll try my best to do it in a reasonable manner like you asked. Let me do this by making a long comparison. Sorry
Opossum
, but I'll be picking on Chrom for a bit to make my point.
If you read through Sakurai's Famitsu article
"Are The Characters Dancing?", you'll see that Sakurai has a very particular way of selecting characters that go into Smash Bros. Chrom in particular was his example of a character that does have the ability to fight, but lacks any qualities that would have made him stand out. While things like a Pair Up mechanic or stance change using swords and lances would have been possible, they aren't core to who
Chrom is, just mechanics from a game Chrom has appeared in. Chrom, in
his core, is a Falchion-wielder that prefers swift, heavy blows with his sword-fighting skills. If
Chrom--not "Fire Emblem Representative #4"--fought in Smash Bros. like he would in his games, he wouldn't have stood out in Smash Bros.'s roster whatsoever. To quote Sakurai:
The movesets in Smash speak for the most part of how these characters would fight in their games. Robin, for example, has no other important character in Fire Emblem combines sword-play with the use of tome magic, all while managing the handicap of a breakable weapon system. He doesn't use the Pair Up as the basis of his moveset, only his Final Smash. The other Lords of Fire Emblem never really have to mind with their legendary blades breaking, which is why he stands with a handicap of losing his weapons from too much use. None of this stretches out what he's like as a character and individual, because fighting this way in Smash is just like how he would in his actual games, both in gameplay and lore. This is why he was chosen over Chrom, who, despite having every potential to be in Smash Bros., lacked the one thing Robin has that he doesn't: a solid concept of his own. Robin's "Tactical Magical Swordsman" versus Chrom's "Marth but more like Ike"--are you even going to argue who stands out in this scenario? The only way something like Chrom's "Pair Up Fighter" would come about is if we ignore what he is first and foremost, turning a blind eye to countless support conversations and events in Awakening's story, and looked at him as part of a duo the way he
can be rather than as the more aggressive successor to the Falchion that he
always is and
always will be.
Compare this to countless other fighters in Smash Bros., whose concept alone is not only
theirs alone of the possible candidates of their series, but already speaks plenty for how they'd fight before you ever hear the moveset. Villager's "Pedestrian Pragmatist", Little Mac's "Stay Grounded and Punish" and WFT's "Fighting to Work-Out" versus Daisy's "Tomboy Flower Power". You know by hearing all of these that Villager would use an unusually non-combative style (like he does in his non-combative game), Little Mac would use a lot of patience in holding his ground before going for a hard blow (again, the entire basis of his gameplay in Punch-Out) and Wii Fit Trainer would strike up a lot of moves with long hit-boxes and quick-succession on part of their stretching and emphasis on exercise (which in itself is a stretch based on their reception in Smash, but still stays true to their practices within their game).
Which brings me into the next topic. These are not only true to their characters in both gameplay and lore, but look at the characters around them--of those
around them, who would sensibly do the same things they do? Further more, of those characters who do the same thing, who would make sense to put in Smash first? The Villager and Little Mac are far from the only characters of their series to do what they do, but as the main protagonists of their series, they get first priority over their friends and rivals. They do these things in Smash not because
their series often does it, however, but because it's precisely what
they do in those series, and by extension, what the other characters in Smash
don't do as well. Same with Robin, who would sensibly be put in before another Magical Swordsman in the Fire Emblem series for reasons of being one of
the main characters. Compare again back to Chrom, who unlike these other characters, didn't get in because what he as an individual not only doesn't shine next to the other characters in Smash, but also doesn't even shine within his own series, where sword-fighting Lords are dime a dozen and we have a solid variety that already cover both elegant and gritty styles.
Now, all of this talk of Chrom? All of it applies directly onto Daisy. All of it.
Sakurai will add a character based on the character itself and what they would feasibly do. For the same reason you wouldn't hand Balloon Fighter a harpoon and rope and say "Here you go, now you can fight in Smash Bros.!", Sakurai wouldn't simply give Daisy an arbitrary party dice-rolling mechanic. Nor a tennis ball to follow around. Nor a motor-bike to ride or a Mario Land power-up to use or just growing flowers out of the ground--that's not what
Daisy is about. Daisy isn't
about these spin-off games. Daisy isn't even the main character of these spin-off games let alone the sole user of their mechanics. Core to Daisy herself, she is a tomboy princess that parallels Peach's girly girl. She's the royalty of a kingdom that essentially no longer exists in any Mario games in the last couple decades, and she sometimes
does a thing and a flower particle effect appears. If you don't ride off entirely turning her moveset into just Mario spin-off things that aren't even exclusive to her, all you have is a Peach clone with slightly more perky and unyielding animations. And that's the problem, being a tomboy and generating flower effects alone doesn't translate into being a moveset. She's in the same circumstance as Chrom lacking a moveset-driving talent, but now
additionally lacking the hierarchy of being a main character to back it up.
What usually happens because of this critical flaw is that Daisy supporters will look to these Mario spin-off titles to fill in all of these gaps... But the issue that a majority of her supporters will look past because of her personality
is left staring the rest of us in the face. A character shouldn't be comprised of these many gaps in the first place, because if their moveset is just left to fill in their character rather than any substance truly of their own, how on earth is that worth a spot over other choices that
do come into the game doing things they can call their own?
tl;dr
Characters are characters, not faces merely to represent mechanics. If the character can't be a character and still be unique, they're not an interesting choice for a character. In a word, mechanically speaking, Daisy offers very little. In Sakurai's words,
she doesn't dance.
