Yeah I'll definitely address why I didn't put those 5 higher.
It would take way too much space to quote all 5 so I'll just name each character and respond to it.
Link:
Link is definitely somewhat susceptible to pressure if you can get in (he would be ridonkulously OP if he wasn't), but even the most mobile characters have to go in cautiously because taking a hit on the way in always leads to huge damage. Link can also afford to be cautious in escaping pressure because he has strong defense (he's heavy and has good recovery) and his punishes hurt a ton. He only needs one touch to do a lot of damage and get you back out, allowing him to start up his keep away game again. Up B and even shield grab are also viable OOS options in some situations.
Mewtwo:
Mewtwo has pretty great (and surprisingly fast) pokes due to his tail, so he doesn't really struggle to rack up damage for his handful of killing moves to connect. UThrow is an amazing kill move on everyone but fast-fallers, and he has other options to deal with them so he can live with that weakness. His recovery is also totally amazing, and he's also great at regaining stage control after being knocked off or above the stage.
Kirby:
The main thing which makes Kirby's cutter dash a decent approach is the fact that he could do the regular final cutter instead. If you try to rush forward and punish it you're risking getting hit by the dash version. The two versions are reactable so you shouldn't go to it all the time but it can be useful in some situations. The strength of Kirby's recovery, edgeguarding, and wall of pain lie in the massive number of jumps that he has, coupled with the option for either vertical or horizontal recovery. Kirby can go super far out for punishes / edgeguards and never have to worry about whether or not he'll make it back. Compare Wario, whose wall of pain is scary on paper but less so in practice simply because he does need to get back onstage at some point. Puff's WoP is still decent but she does need to actually hit someone first, and she has far less options for doing that than Kirby does.
Sheik:
I think you're somewhat overthinking Sheik. She's still fast, strong, and has ridiculous combos on most of the cast. It's true that she's lost a bit since Melee (which is why I moved her down to upper mid), but she's still fairly scary.
Zelda:
Zelda isn't totally one-dimensional, though, she also has good tilts, smash attacks, and aerials. Zelda is actually exactly the kind of character I wish Samus was. If Samus could frustrate you with projectiles and then deal big damage with normals or kill you around 100-110% I'd have no problem with her.
frame 15 would be 5 frames slower than melee.
also, I HIGHLY disagree with samus being multi-dimensional. the only way she makes people approach is with missles and then she plays her annoying attrition game with jabs and f-tilt. sometimes throws in a grab too.
she keeps playing that game over and over again until she gets enough % for d-smash to kill.
her punishes are weak and don't guarantee a kill until like 150% unless charge shot of course.
This is pretty much my opinion on Samus too. Poking / projectile game is good, but her offensive options beyond that seem very limited. None of her aerials have any killing power, it's pretty much charge shot, Dsmash, or Dtilt that has to do the job. Her survivability also isn't the absolute best because she's easily killed off the top due to her floatiness.
This is why I'd like to see buffs to Ice Beam. I think the way it should work is that Fire Beam = damage building while Ice Beam = kill power. That would make her offense far more dangerous once you got to higher percents. I'd also like to see some buffs to throw followups to better reward the fact that her throw is quite hard to land.
way back in 2.5 iirc, GnW won a tournament before Mario did.
Wasn't G&W much better in 2.5 though? Of course, he had fewer characters to contend with back then, too.