I know I´m not from this region, but i stumbled upon this thread and was quite intruiged by the OP. I havent read all of these posts, so forgive me if I am reitterating what has already been said by another member of the community.
My experience with smash is that we all plateau regardless of how hard we may try to improve. There are just certain people that have it, and others dont. You rarely ever see someone who has been in the game for years all of a sudden rise to the top, but you do often see a person come from what seems like out of no where all of a sudden progressing quickly to a peak. I dont wanna say that they immediately become pro, but it takes very little time, and they usually go from nobody to somebody pretty quick (less than 2 years lets say). We usually refer to these people as prodigies, and we´ve have a ton of them. Chillin, PC, m2k, mango, Cactuar, Scar, Jman, Armada, Hbox, shiz, colbol, etc etc. Nowadays it seems like all of the vets are replaced by young kids whos learning curve is amazing, and their natural talent seems unfairly strong. Most of them think and play quite fast, have amazing reaction time, think extremely well under pressure, etc.
Ive often said that Smash at its highest level, like many sports and competetive games, is really a either you have it or you dont kinda deal. If you´ve always found that your progression was slow and steady, chances are you´re probably never gonna make it to the top. Its a sad but true phenomenon about competition.
So to answer the question in the OP, I feel that you really cant do much to greatly improve. However, there are things you can do to make a pretty significant difference. Im going to use myself as an example.
When I was a Fox main, I found that I simply didnt have the raw talent in my fingers to control Fox the way people like Colbol or Jman are able to control him. Fox is like a ball of chaos that only a small number of talented individuals are fast enough to control, and I was not one of them. I found that my success came only when I out-thought my opponent greatly. I made numerous mistakes every game (regardless of how much tech skill practice i put in) which gave my opponent tons of openings to put on big punishes (and we all know that most of the cast can punish fox pretty hard given the chance)
I decided to change my main to peach just for fun, cuz I was bored of fox. I completely dropped him all together, and just started messing around with peach. I found that some of my tech skill practice transfered over so that I was able to move quite fast with Peach because I had practiced so much with Fox. This was amazing to me because I was always a ´slower´ player. I found that with more control I was able to be a stronger competitor. In addition, I simply found that maining a new character gave me all kinds of new insight into melee.
So I find that using new characters is one of the best ways to grow as a player mentally. Often times u find that you are actually better suited to play a character other than your main, and that your skills shine through when you try other characters. I personally find it very hard to pick up a new character unless I completely devote myself to that character for quite some time (slow learner i guess, mostly tech skill problems =/ )
So if you ever find yourself plateau-ing, and you are determined to improve, try picking up a new character. You may move your plateau up a notch or two. But remember that most of the time this stuff is kinda set in stone, so dont be too surprised that you dont just shoot up to the top just cuz u start making good headway. In the end you will certainly have grown as a player, but there will most likely be new prodigies popping up all the time, so you may end up back to where you were, lol.
