Okay, let me raise legitimate arguments on certain stages for a little bit here:
Mario Galaxy: It is not your typical walk-off stage, and yes, despite you being able to walk off, there's an extremely far distance to try walking off. Also, look at the shape of the stage itself; the stage shape is very different from a straight-forward walk-off, as the edges seem to act sort of like "edges" on non-walk-off stages. While people may concern themselves with camping on one end of the stage, there's the thing, this stage has the largest walk-off lines out of any walk-off stage, and it takes literally forever to actually KO someone by camping near the edge.
Mushroom Kingdom U: Nabbit often comes randomly or during a second phase or third phase (I don't know when), but whenever I see Nabbit, instinctively I'd want to KO him as fast as possible. Now the stage transitions after a very long amount of time, which means the chances of seeing Nabbit, if he's at random, are also lowered since the stage takes nearly forever to go to the next part. None of the parts actually contain anything that can be considerably bannable, all except for Nabbit, who can just be simply KO'd or better yet, escaped from. Since we have the best method (multi-button mashing) of releasing your character from grab status, it'd be easy to get away from Nabbit if he captures you.
Jungle Hijinx: Alright, fair point, but the stage is otherwise balanced with everything else. The blast zones are only wonky because the stage is unique to the series in that it's a foreground and background stage. Also, on the first point, circle camping is actually relatively impossible for this, as the foreground and background sink after a certain period of time that you are on the stage, so you're going to have to be on one side of the stage or the other. Furthermore, there's the pillars that suddenly pop up or the cannons blowing up that ultimately destroy any chance of circle camping. Heck, even the cannons leaving off screen and the layout of the stage prevents circle camping.
Kongo Jungle 64: Wow, a stage that has so many platforms to jump on is able to circle camp? Even though the stage clearly is impossible to? That's my question to ask, how is it remotely possible to circle camp on this otherwise balanced and neutral stage that you can't circle camp in? There's two middle platforms and two top platforms, as well as a bottom one and a barrel. It's not very likely, if at all, you'd be able to circle camp unless your character has high jumping prowess over a character like Little Mac, and even then, opponents may predict where you're going, opponents may have projectiles, opponents have a lot up their sleeve to prevent it. It's actually hard to circle camp on this stage, it's not easy.
Skyloft: That's the same exact concept as Delfino Plaza, but this stage has more fairness into it, and it's not random to save you. Random means that it's not choreographed in any fathomable way possible. Skyloft is actually very linear in there it goes, and you will know where it goes when you see it, too. All parts of the stage are balanced, even the walk-off portions, as you'll get punished when the platform arrives back on stage on a walk-off portion and camp there, making you an easy target to KO afterward. There's not many places that can "save" your opponent if you know how long it takes to transition from one place to another, or if you can just simply KO them off the side or the top blast lines.
Hyrule Castle: The cave of life in this stage is very...small. So small and avoidable as well, and it has only one direction, vertical. So a simple horizontal attack in this "cave of life" is enough to destroy your opponent. The stage has huge blast lines, but it's not like it can't be fixed by using characters with relatively high KO prowess, sticking by the edges of the stage or going for bottom blast zone KOs or off stage KOs. The two hazards on the stage are actually very predictable unlike their Smash 64 counterparts, which could have turned very fast. You may argue that they are powerful, but only if they make contact with you. Like many other things I've talked about, they come out at a relatively preset time, as well, so worrying about these hazards is nothing unless your opponent actually starts throwing you into them, or in Ganondorf's case, F-Tilting you.
Pokemon Stadium 2: While true that the wind portion of the stage is very harmful to one, you can't just let one part of a stage ruin a stage for you. This stage, while having transformations, also has a balanced platform on it at the start, and the transformations are all random at best. The wind portion of the stage only applies on stage, I believe too, but correct me if I'm wrong on that. While it is a controversial stage at best, it could at least be a counterpick.
Skyworld: Okay, this is a good excuse. These are actual things that convince me of it being banned since it is actually an unfair stage at times. Next.
Wrecking Crew: How do you defeat this stage's circle camping? The hazards themselves or just by going up or down. That's it. The stage has nothing else wrong with it. The idea that you can circle camp in this stage is beyond me when you have characters like Falco go against someone like Diddy Kong or Sheik. Falco can easily jump high enough to reach the two if they try circle camping, for example, and even if they go off the edge of the soft platforms, remember, they are SOFT platforms, so you can just tap down and boom, you're at where the opponent will be if you hold down. Circle camping on this stage is very, very hard because there's literally only one way you can, and it will often times backfire if your opponent can tell very well.
Pilotwings: There...is the inability...to circle camp on this stage...whatsoever. The stage layout is just two planes, that's it, one with soft platforms on the top and one with just one single, Final Destination-like platform that tilts like Lylat Cruise. So if it tilts like Lylat Cruise, that also removes the ability to efficiently camp with projectiles. The other sides of the stage are NOT unreachable, you can actually reach them quite well if you have the patience, the skill to perfect shield and the will to go. If you're close enough, bait your opponent to jump and they will jump above you, where you can hit them. Camping and having unreachable camp spots aren't the problem. Even the plane with the soft platform has no really unreachable camping spots, despite there being a bottom portion to the stage. If there was really a problem with circle camping or just campable spots, there'd be some evidence supporting this, but with projectiles being mostly linear and the stage tilting, I find it hard to believe that there's actual unreachable camping spots, and with the entire cast (except Villager) being unable to go under the planes or successfully over one another (if they are projectile camping), Circle Camping is also hard to believe here.
Wuhu Island: They banned it because of a glitch that was patched and applied to a very specific section of one section, the boat. The stage has the "we have Delfino so we don't need it" argument as well to it, but that's not a good argument to go with. The stage has 3 walk-offs, one of which in particular has two lower blast zone points (the bridge), but the stage transitions so there's no need to be worried about them.
Windy Hill Zone: But remember, this stage has platforms, and what do we know about trying to run away on a stage that has platforms even if it's large? You can jump on the platforms, bait or wait, then retaliate accordingly. Also, a character like Falco can beat anyone trying to escape by trying to run away from a high vantage point through jumping. Now in the case of a character like Sonic fighting Ganondorf, running away somewhat applies, but remember, it's not impossible to wait or bait an opponent. Plus, a character like Link or Samus could easily find ways to beat opponents running away and get the opponent toward them. If you're in the lead, you'll want to get a stock or defeat your opponent just to ensure your lead or win.