Ridley is a strange design since he seems to be designed as a heavyweight fighter without the overall raw power or knockback resistance of one. In return, he's quite fast for a heavyweight fighter, and has multiple jumps. The problem is that he's fast...for a heavyweight fighter. It makes sense because his mobility likely wasn't meant to be a strength in an of itself, but rather in conjunction with other heavy traits like big buttons that allow you to smother your opponent in advantage. This is something that he does well, but if he's not able to get things going, this tradeoff becomes more of a weakness than a strength, and it will always be a limiting factor for his game plan.
More than that though, he suffers from a very unbalanced moveset within its own context. It's not Zelda tier where she only has, like, 3 good moves amongst a pile of pretty crappy ones, but it does allow for certain attacks to take over the moveset when playing, and not in a way that feels intentional like with Duck Hunt's Trick Shot. Characters with this issue tend not to feel great, and this is made worse by some wonky animations that come from a clunky workaround with his logical range. His forward aerial, for example, is very needlessly cramped feeling just because they didn't actually want him to extend his tail very far and add a ton of rang to it.
Then there's Wing Blitz. Why is it not omni-directional? Why do I have to go backward if I want to go up and to the side? I get that they wanted to make it unique, and this is basically just Fire Fox with some changes, and heavy characters are supposed to have a limited recovery but for one, Fire Fox is a limited recovery move, and for two, Ridley is supposed to be an aerial based character. Making his recovery move so awkward to control makes detracts from his fantasy of being most at home in the air. And it's not like it wouldn't be unique after that either since a single hit Fire Fox that spikes when you angle it downward would be super cool.
Lastly...Why does he not have pogo tail? This is like his most notable attack, even more so than his plasma breath. Why is it not here in any form? Why is his down aerial a really slow stall-and-fall stomp with his feet? If I were to change 1 thing about the character, I would make his down aerial a downward tail stab. The move would spike at the tip, and if he hits the ground, a shield, or an opponent with it, he bounces upward. If he hits the ground with it, not only does he bounce upward, he regains his double jumps, allowing him to stay in the air longer. If you really want him to keep the stall-and-fall, at least make it like Raptor Boost where he travels down, and then when either the ground or an opponent gets into range, he stabs them, with the same or similar benefits as before. With this version of the move you could even throw in the ability to do 1-2 extra ground stabs to mixup punish timings. You could also combine the two ideas, allowing Ridley to choose whether to do a regular down aerial, or to stall-and-fall based on whether or not the player is still holding the button at the end of the start lag. This would be a very simple way of establishing his air superiority by giving him more control of his aerial mobility and disadvantage state.
While I mostly talked about what's weird about him, I think Ridley's design is actually pretty decent. The main problem I see is that it just wasn't pushed far enough, and not even in a "he needs gimmicks" kinda way. His strength tradeoffs don't quite balance themselves out enough for him to be as effective as he was intended to be, and his kit is poorly balanced in regards to itself. He also just has a few oddities that work against the fun he was supposed to allow you to have. I always thought it would be cool if he had a flight mechanic that was sort of a combination of Float and Robo Burner, but all he really needs is some rebalancing of how useful his tools are, and a new Link or Greninja-esque down aerial.