The point was that it's all Demise legitimately has going for him... not that it actually made him likely. It just makes him the only actual potential Ganondorf clone at best. Which doesn't help that much. I never thought he had a chance either. But really, the idea of getting any new Zelda characters is really damn unlikely too(even with enough recurring or important characters who have the merits to easily get in).
And no, it's more Toon Zelda really has not gotten any actual major skills that isn't already covered by Zelda in the first place. It's not just the Phantom. The Light Arrows is meaningless as other Zeldas already do so and nobody knows what the hell the Light Force is, the only other thing that was major to her. All three of her stuff doesn't really help at that point. Being a clone of the current Zelda works, sure. But that time had come and gone too. And we know Hyrule Warriors isn't really something to rely on for, well, anything but a Spirit(or Trophy-type thing) at this point. ...That, and it was Phantom-based too. If they start bothering to give her more defined skills, it'd be easier to see her have a real chance of making it in. Right now, her most notable and more importantly, defined, skills are pretty much already covered. Bar, again, a clone type, which isn't really why people even want her, heh. Also, keep in mind she was only considered due to being a clone type for regular Zelda, and that's including with a transformation into an OC with Toon Sheik. To say the least, that's not boding well for her.
...Did I miss Tetra, actually? Best thing to say is; she's certainly got potential, but there's nothing to suggest she was actually ever considered at this point, and she didn't actually fight outside of HW(which we know isn't a reliable source of moveset references). She also cannot be some kind of easy Echo(though yes, she could use Toon Link as a body base to help create, but Sakurai first would need to have an idea of how he wants her to play).
We also have to look at other factors to why things went the way they did; Zelda in general didn't really fight in games(and still barely does without some very major caveat, like the Phantom being the actual playable character), so it wasn't surprising that Sheik already was created due to having some semblance of moves, but also we knew she was able to fight in the game. Zelda also in Melee does not resemble nearly any of her official abilities except Transform and a minor ability to move things around with her mind(her grab mechanic isn't really much different from how she uses magic to open a door. And you could still call it a stretch). A lot of other versions of Zelda(not her forms like Tetra etc.) still suffer from this, with very few moves. BOTW is definitely an exception... but was dismissed anyway as an option to change the current Smash Zelda into(though TOTK Zelda, who is a completely different character in everything but name only, isn't entirely off the table as a newcomer if you want someone who actually has something new to add outright).
This also kind of shows why the Zelda franchise has gotten little. Zelda herself actually was lucky to get in, since the gameplay mechanic made her much easier to work in. Sheik already was actually easy to make in comparison. You don't need much to make a ninja at that point, who we know actually outright fights design-wise. Also, it's worth noting that Zelda's inclusion was also hidden during some materials where Sheik's was not. That said, there's also one other prerelease CSS that is impossible to discern due to massively bad quality(It didn't appear to have Sheik on it yet, though). It had only 13 characters at the time.
But yeah, I'm pessimistic due to how the franchise's playable representation is handled in a pretty bare minimum approach with many quite lucky to get in. Though at least Toon Link was actually planned from the start, but even then, he still is lucky due to using Young Link's assets too(if Young Link didn't make it in? Toon Link probably would not have). Leaving two characters who were easy to add on their own merits/without some caveats doesn't help.