To expand on what Bubba is saying, the problem is that by keeping the spacies the same and/or "untouchable", they will inevitably be the top no matter what.
For example, Ike was considered on their level, the community cried out and now he's gotten tweaked for better or worse. Lucario has gotten OHC changes and the KB Stacking will definitely effect him, and many people saw him as on par with the tops as well. All this while Fox/Falco are left the same, characters approaching their level seem to be getting swatted down to the Falcon/Marth level. Still good, but compared to the S tier?
In return, many characters are simply given anti-spacey tools which can lead to collateral damage. For one, as Bubba said this hurts Falcon and Wolf (probably any fast faller really) unfairly as the anti-Fox/Falco tactics will also work on them, and many of the tactics such as CG's etc lead to kinda boring gameplay. Two, if everybody is just given anti-space animal tools it will make MUs vs the Spacey kinda one dimensional as it'd be the Space Animal vs the Up Air Juggle instead of Fox vs Whoever. Yes, this is a nerf by proxy, but at the cost of it seeping out to other MUs as well as altering the gameplay against the intended targets in what may become an unfavorable manner.
With more characters incoming, at a glance none of them really seem to be on par with them, especially as Sheik has been tweaked to be a tad less overwhelming, and Jiggs has just either gone out of favor from what I've seen / grown natural bad MUs. Those changes (while controversial for Sheik) seem to have ironed half the top tier out to the desired level, but Fox and Falco are still a step above the rest.
Wouldn't it make more sense to eventually tweak them a bit to not require everybody having Anti-spacy tools, while still retaining their feel?
