Literally every meteor apart from Ganon's dair is techable on the ground. Also her dair autocancels as well as combos way later than utilt on the ground. Sure it's not probably better than C or D, but it's got some uses you're ignoring.
Not true. There are plenty of meteors that are un-techable, Ryu's being the absolute best, but you can go down the list. To further the point Falco's D-air was patched to go from techable to un-techable so it's specifically introduced as a "balance" aspect of the character.
Take a short character like Pika, pick any character and input a shorthop and immediately d-air to try and hit Pika. There are only 2 characters in the game that will miss, Ryu, who has a fantastic d-air, and Samus, who has a terrible d-air. With Samus you have to rise and then come down and to hit the autocancel window in the middle of a fight with a skilled opponent is hard. And this isn't just Pika, there are tons, and tons of crouching animations from taller characters where this move just whiffs. It's like a 40 frame move in neutral out of a shorthop. It's really awful - designed to be awful.
I would take Palutena's frame 10 single active hitbox any day.
If Monkey flip and ABK are S-tier, I would say Dancing blade is likely A-tier.
Corrin Dragon Lunge is either S or A, I would say S, too much utility, too many options to be A-level.
On the other end of the spectrum if Samus side b is F, probably my vote for E would be MK drill rush. It's basically a last ditch recovery move but doesn't have much else going for it as a frame 26, 1 point of damage move. It's just, bad.