The first problem I have with your argument is that there is no defined way to play the game.
At its core, there is an
efficient way to play the game. When I refer to a back-and-forth with neutral games and advantageous positions, that is the only method to play a competitive level because people will shift towards the most efficient way of playing in order to win.
You state the game is "about skill with their characters" and even disregard adaptation.
Adaptation and knowledge (of static stages or otherwise) falls under player skill. If we call ZeRo the most skilled player in the world, it's a reference to his ability to download playstyles, his knowledge of combos and movies, his technical skill, and so on.
I might've misworded it in my post, but I'm referring to all of these things, including adapting to scenarios/strings/combos presented on static stages like Battlefield.
Why is adaptation not a good skill to have? Why is a dynamic stage bad? On most stages you can use these changes for your own advantage, specially if you can capitalize on the fact your opponent didn't, why is not a good skill to have to be able control the better terrain?
I addressed this. Being able to adapt to a stage offers no assurance that it can't bite you anyway. Players do not play on the stage's clock, as doing so is inefficient because the bigger threat is the sentient opponent. Hence, the stage hazards can be random relative to the player vs. player combat going on. A random Shy Guy car may not
hit you, but it can force you back into a neutral game you had already won. That's punishing you for nothing.
...Which can happen to either player. The idea of a counterpick is that it provides a specific benefit to the player who chooses it, mainly through character matchups linked to specific stages. In Mario Circuit, there is no inherent advantage, and whatever thing you're capitalizing on wasn't something you actually earned if you threw them into the wall because the stage was right there at the time.
So even if you can adequately adapt to stages in certain situations you cannot 100% of the time adapt because the demands of the stage and the gameplay the game demands are at a conflict. There will be scenarios on stages like Kalos, Port Town, Circuit, Kingdom U, etc which are unavoidable and provide disproportionate advantage for what otherwise would've just been a neutral game you won.
It's not as bad when the non-static "randomish" elements are completely mundane since usually you get second chances without insane punishments. Randall in Melee on Yoshi's Story is a good example. It can save players on an edgeguard, but the player it saved is still at a serious disadvantage rather than Randall outright resetting the position of both players.
I think it would even change the dynamics of when to approach or when it is safer to throw a move.
The point is that the whole game would be much different, and that's not necessarily bad as you seemed to point out.
The difference is that the competitive aspect becomes PvE+P, yet the game isn't built or suited for that in a way that allows it to remain totally skill based. You can have a lot of stage knowledge and it can benefit you in a skillful way, but the conclusion is that it has a ceiling as to how skilled/adaptive it can be before what more or less amounts to a dice roll kicks in and sometimes you're punished for circumstances beyond your control even if you have an intricate knowledge of the stage and played well.
This is fine and all but it's clearly not what the majority of the competitive community wants. I say that people should get together, create a well-reasoned argument as to why they want a game that involves more stage interaction, and try and build something from there. If the support exists, you can go as far as side events at majors with extended stage lists emphasizing the alternative style of play. If you really do have a point on certain stages being viable but unlooked at, it might grab people's attention.
if we keep this trend to reduce the stagelist, as it becomes repetitive people will lose interest in this game
Every other Smash game has survived on highly limited stage lists. If the game reduces in popularity in the next two years it will be because the character meta (i.e. what most people play the game for) has become stale/tired for people, not the stagelists.
You can quote me that if the game has a significant falloff it will be because the meta evolves to a point where only 4-5 characters are viable and the game becomes exceedingly campy/slow. Given Sm4sh isn't Brawl, I'd like to think we're relatively safe from this, because even our worst (Sheik) isn't showing the intricate level of rule-change needing dominance Meta Knight had, and we lack the janky Chaingrab nonsense that made characters like Ice Climbers so absurd.