I agree with your reasoning in general, but is Kongo Jungle 64 really more match-up polarizing than Halberd? Or are you talking about Little Mac specifically?
My experience with those stages is that Kongo Jungle 64 is generally really bad for some characters while Halberd is really good for some other characters. Maybe there are match-ups that I've missed but a dedicated Little Mac main can always ban Kongo Jungle 64 because he/she knows what character he/she will play, but you can never be completely sure which character your opponent will pick in game 2 and 3, meaning that you can't safely know if you should ban Halberd or not.
My point is: Aren't the polarizing match-ups on Kongo Jungle 64 less relevant than the polarizing match-ups on Halberd?
A lot of run-away tactics are pretty strong on Kongo. People in this topic who are talking like the run-away is unbeatable, to me, seem like they don't have enough experience on the stage; unless you are literally using Little Mac, it's possible to catch people on KJ. It's really not like Temple at all. That being said, catching people can be hard, and that can give people some solid advantages. The really huge blastzones relative to every other stage are also about equally polarizing to Halberd's small blastzones so, when everything is put together, Kongo is clearly more polarizing than Halberd. That being said, with appropriate stage procedure, you can play around Kongo well enough that it doesn't really make problems for tournaments that use it since plenty of MUs are fine on Kongo.
Routa
No you can't, or you don't understand what circle camping is. None of the legal stages have platforms that are hard to reach like KJ has.
Agreed that it's more a natural selection than thorough research, but you shouldn't be too quick to come to the conclusion that no one has put any thought into it besides following what the top players said.
That's just your biased opinion towards stage conservatives. What you see as "a game mechanic I don't want to understand" can be seen as "an intrusion that doesn't fit my ideal competitive scenario" and while both are subjective the second one isn't nearly as lazy.
It's a common misconception that when people don't want to play on a janky stage it's because they're too lazy to learn how it works. Maybe it's the case for stupid people, but there also are intelligent people that do not want to play on Halberd because they do not want the outcome of a match to depend on who the laser/claw targets. Some stage features are simply too intrusive for those people and I understand them. There is nothing wrong for not wanting the result of a tournament to depend on things like Delfino's ceiling changes.
And people did not give Peach's Castle a chance because the bottom platform clearly gives a positional advantage, and if you want to approach someone that's camping there you have to take an absurd amount of risks.
There's a lot of baggage to address here.
I'm not convinced the term "intrusion" means any more than "jank". What defines an element that is intruding versus one that is a "natural" part of the game? If there were no stage, everyone would just fall off the bottom blast zone and the winner would be whoever can stall in the air the most. Is the ground not interfering with that? Do platforms interfere with movement by the same logic? How is a ceiling's position an interference? If Delfino has a low ceiling at one time, maybe it is an interference that Final Destination does not. If I really like platforms, can I call it an interference that Final Destination doesn't have them since it's interfering with my natural game plan?
What you said about Peach's Castle sums it up for me. Of course being on the bottom (and in the center) offers you a positional advantage. Being in the middle of Final Destination offers you an advantage. Standing under BF's platforms can offer you an advantage. Charizard standing under Duck Hunt's tree can get a great advantage with his uthrow. Getting positional advantages by exploiting stage features is a core aspect of smash gameplay, and all players on all stages will be doing it all of the time. I just don't understand the alleged difference between what moving and transforming stages have and what static stages have. When I play, I don't use a different mental process to decide "I should stand under a platform" versus deciding "I should move the Halberd laser targeting me to the ledge". It's all just stage position optimization based on the current context. To me, static stages are intrinsically more egregious than moving ones because moving stages don't allow anyone to become entrenched in a position and offer different characters different advantages at different times while static stages allow for the really big advantages.
It just seems really arbitrary to me to decide some stage elements are "bad", "janky", "interfering", or whatever words will be used. I see stages have several real impacts on matches: they offer character advantages/disadvantages, they can have random elements that increase match variance, and they can (if particularly poorly designed) cause slippery slope wherein whoever is winning has a big advantage over whoever is losing (Jungle Hijinx is the main stage with this strange and undesirable property). To me, as long as a stage is reasonably well balanced across match-ups and reasonably non-swingy, it should be legal. I am totally unconvinced Delfino or Skyloft or any of those are more swingy than static stages, and I'm entirely convinced they're actually more character balanced.
Genuine question here because I'm curious : you must have played with both typs of stage lists (13 with FLSS and short with only 5/7 stages) ; do you observe a change in competitive results ? Are there people that get better with a bigger stage list or inversely ?
I wish I could give a better answer than the truth. The truth is that our city is very large so events in different areas of the city (with the different TOs) often have pretty different pools of players which limits my ability to gather that data; I can only think of a relative handful of players who have traveled around a bit more. Largely it only comes into play in two situations: a player is really unfamiliar with stages that are legal or a stage list has so few and such poorly selected starters that it really screws someone's main. I've counterpicked Skyloft on people who responed with "I don't know what that stage does", and they always predictably play pretty badly on it (somehow I never feel guilty; if I think they don't know all of the stages well, I'm going to ignore character advantages and go for something I suspect they aren't familiar with without hesitation). On the other side, we have had several local tournaments that had the starter list of FD/BF/SV/T&C/DL. This really hurts our local Sonics since Sonic is really disadvantaged by three of those stages; as long as the opponent is smart enough to strike FD and T&C, Sonic is forced to a bad stage game one which really does cause those players to lose to people they should beat.
Well that's just your experience, mine is the complete opposite and I've both seen and lived stupid stuff on every stage but smash ville. The worst this stage has is early kills when the platform reaches its stopping point and increased follow ups from a throw when it's performed from the moving platform. In all cases it's way less offensive than being killed by a blastzone size change.
Have you ever seen someone use the Smashville camping strategy? Use a character with a good grab game and fight against someone who has a bad (or non-existent) projectile and a lackluster ability to approach from the air. Get a 30% or more lead, get on the platform, stay on the platform, and start playing for a time-out. The movement of the platform makes it way easier to keep up for a long time, way stronger than sitting on a non-moving platform on BF or something. It's really dumb, and it makes a lot of MUs really stupid. If you thought Sonic was good on SV in my previous paragraph, this is why he's not (his ability to deal with this is one of the worst). I'm always amazed at how rarely people do this, and I'm always amazed at how powerful this is for me when I go for it. Combined with the (substantial) other shenanigans that platform allows (and how strongly character polarizing it is), I see it as the stage of all plausibly legal stages most likely to produce poor gameplay. I really don't think it should be banned, but I don't think it's much better than "good enough".