All I can say is that I see a distinct lack of discussion about crouch cancel in this thread. Half the reason a lot of low tier characters are low tier is because they are awful against crouch cancelling. One key part about all the top tiers is that they have good, reliable, and sometimes even easy ways to deal with a crouch cancelling opponent (drill/shine, drill/shine, needles/amazing grab, dair/amazing grab/spacing, tornado dress/float cancel/turnips, stomp/knee/grab, death grab/fair, spaced bair/dair/decent grab).
I am fairly certain YL cannot fair -> d-smash safely against crouch cancel. A quick look at his frame data thread shows that he has 7 frames of lag after the fair and his d-smash hits on frame 9. That means it will hit on frame 16, earliest. A crouch cancelled move applies 4 frames of "stun" (really just landing animation that in most (all?) cases can be cancelled on or after 4 frames - we'll assume after because I forget). 1 frame before the d-smash hits is frame 15. After 4 frames of the landing animation, there is still 11 frames before the d-smash hits. That is enough for Link to grab if he is frame perfect. I can assure you that other characters will grab you by that time with ease (4 extra frames of leniency). You could space it, sure, but 11 frames to shield is practically impossible to mess up. Also consider shine which will have 11 frames of leniency assuming you don't space properly.
Bomb drop OOS is NOT 1 frame. It is jump squat + 1 frame. It's essentially as fast as a shine OOS, but shines are safe against CC at 0%. A spacy trying to shine you will most likely CC the fuse burn (because they are holding down) and then still shine you. Even if he gets stuck from the bomb exploding (it might not because it bounces around a bit when it burns so the shine may miss), you still got knocked down (if fox) or launched (falco).
OOS options are nice, but consider how they are against CC as well. The reason someone like Link can get rushed down is not just because he has slow OOS options, it's that none of them are safe against someone holding down. It is the same issue for YL, but at least he can wavedash much more quickly. Otherwise, it is safe to say that they both essentially have no moves OOS (without shield dropping), as long as their opponent is at low damage, that are safe.
How is Pichu's nair against CC? I can't say I know, but I have a hunch that CC -> almost anything will punish it quite easily. Either that or it will mean that it is basically neutral again since your opponent has no stun. There is also the issue of the opponent going for trades - much like how Ganon is heavier than almost everyone, Pichu makes everyone else the Ganon in the matchup. He just loses at trading.
One of the main reasons Ganon is any good is because he can actually crush a CCing opponent. His stomp is like a super punish to it, but even a spaced fair is quite safe. His high knockback also removes it as a viable option against his weaker moves quite early. He has decent mixups with platform movement. Spaced moves on shields are safe. If you trade with him, you are losing. He even has his jab which is quite good against CC and comes out ridiculously fast. A good panic button (unlike YL, Pichu, or really any low tier).
The biggest factor to consider when you want to threaten space is how to deal with an opponent holding down. Ganon threatens against CC starting from 0%. What can YL do when his opponent is at 0%? What can Pichu do?