It sounds like you want characters to be more homogenized, not simpler.
I can see that homogeneity would be a side effect of simplifying the characters' moveset designs to 64/Melee standards. And honestly,
so be it. I came to the conclusion in a
discussion about three years ago that
a bit of homogeneity played a role in Ultimate's character balance being better than Brawl's and Smash 4's. While my complaints with the outlandishness of several (though not all, admittedly) Smash 4-on newcomers has little to do with balance, I'm willing to accept the characters having similar functions for similar move inputs if it makes the characters more intuitive. Playing 64, Melee, and even Brawl, I had so much fun constantly changing the character I used with every vs match (human or CPU) or single-player mode run, while with Smash 4 and especially Ultimate, I find myself trying out a newcomer once, then gravitate back to the 64-Brawl characters again and again.
Besides, most agree nowadays that even in Melee's clones having similar move functions and straight-up sharing animations for the most part, even they end up playing very differently from one another. I'd argue that, as I mentioned before, setting Brawl Snake as the upper limit for character complexity would breed creativity, not stifle it.
"Palutena's Up Smash is big." Is something casuals figure out in seconds. It's simple to understand. It's less complicated then Link's Bombs or Mario's Cape or Jigglypuff's Rest.
Arguing normal shouldn't have those kind of special qualities is arbitrary. Especially since Melee and 64 already have tons of oddities with their normals. For examples, Ness' yo-yo, Peach's F Smash, and Marth and Roy in general.
I understand characters like Shulk, Ryu and Kazuya are complicated and potentially intimidating.
But when your examples are Villager and Palutena? Two straight forward and easy to understand characters? Casuals are not braindead. They can look at something slightly different and put two and two together.
This sounds like a you problem, not so much a game design problem.
Characters being a lot harder to pick up and play due to their complicated mechanics is, again, only half my problem with the Smash 4-on newcomers' moveset designs.
Sure, Palutena's Up Smash being really tall is easy to understand, but really, the other part of the problem is that it's making the "special" moves... just not feel special anymore. You mention moves like Ness's Down and Up Smashes and Peach's F Smash, but Ness's charging hitbox felt like an easter egg since the release still feels like the "meat" of the move, and it's quite telling that Peach's Forward Smash got its RNG removed. Even then, the 64, Melee, and even Brawl newcomers felt like they had
some limit on putting those moves in the game, nothing like Min Min feeling like an ARMS character plopped in Smash's engine rather than a Smash character making careful and deliberate homage to their source material.
If Mario were a Smash 4-on newcomer, he'd be using a mishmash of different powerups from many different platformers rather than be a hand-to-hand shoto adapted to Smash's engine. If Meta Knight were a Smash 4-on newcomer, he would have his Crescent Shot on his Forward Smash and his Tornado Slash on his Down Smash. And those are just dumb ideas.