Just finished watching that video and reading most of your excerpts. Not usually a guy to dole out general Smash Bros. self-improvement advice, but I think I can still offer some insight here.
I'm gonna suggest something rather extreme and out there, so keep an open mind about this. This isn't a jab at you either or an attempt to get under your skin. It's just a different perspective you ought to consider. And I may be way off base and looking too deeply into your issue. But maybe not.
I'm also very long-winded, so brace yourself.
. . .
You might need to take everything you currently know regarding Smash Bros. ... and BURY IT!
Yeah I think that's the best way to put it. Trash it, burn it, tear it into little pieces and throw it into the wind. Strongly consider starting from scratch.
Let me explain further using an analogy: You're a swordsman who finds himself at the proverbial bottom of the barrel among your sword-wielding peers. You want to achieve greatness, get out of this slump, and be acknowledged as a respectable swordsman at the very least. So you're inquiring from other swordsman what they do to win. You study other successful swordsman and try and pick up new ideas. You train with friends and acquaintances. You even attend tournaments, but you struggle to apply what you've learned. One day, a random person walks up to you and challenges you to a match. You quickly accept, draw your sword, have full intent to win... and you get disarmed and dropped flat on your back in an instant. You're stunned that you could be taken down so fast. Then you're downright flabbergasted when you realize your opponent
was completely unarmed, physically frail, and half your height! What in the heck happened? You can only muster the words "HOW?" This half-pint of a person's response?
"My only concern was the sword itself, and you failed to even point it in my direction. Thus the one obstacle in my way was removed with zero effort on my part."
Excuse the lengthy short story. But it has a point. As far as I can tell, at some point the very fundamental core of your play kind of became a mockery of itself. A farce. And it's definitely illustrated in what you and other people have mentioned: That so-called dash dancing. But not just that, but practically everything you were doing in that match seemed like a poor imitation of what Smash player wants to do. You can dash left and right, so you did that. You have an Up Special, so you did that. You have some other attacks, so let's just do that too. And at almost no point in those matches did I believe you actually knew
why you were doing that nor were you concerned about your opponent. That goes far beyond tournament nerves. I saw a complete lack of awareness beyond the reach of that Zelda. Not
your Zelda. Just "a Zelda".
No game plan, no awareness, no identity, no real goal, no point. You understand juuuust enough to eventually take an opponent's stock. But that's everybody else, and they happen to grasp the "how".
This is why I'm suggesting to start from scratch. It's one thing to know how to play. It's another to know how to WIN. You can't do that by picking up tactics from other successful players without knowing
why they do it. You can't throw out attacks for their own sake. You can't fight on equal grounds with any opponent when subconsciously they become a Sandbag that happens to hit back.
But how does one begin anew when they've played Smash Bros. so long??? You'll have to discard everything you
believe you know about Smash. The tips you've picked up, the ideas you've integrated into your game, even the character you sought to main. None of it does any good when it's all situated on a foundation of wet sand and water. Proper fundamentals rest upon a strong, sturdy foundation. You can acquire all the knowledge you like (combos, advanced tech, matchup data, dexterity), and then you store that knowledge in a house that crumbles against a light breeze, and then what is it all worth?
Neutral.
Spacing.
Defense.
Advantage.
Disadvantage.
Edgeguarding.
Recovery.
Mix Ups.
Reaction.
Reads.
Rededicate yourself to these disciplines. Start fresh with a fundamental-friendly character. Zelda is not fundamentally friendly. A well-rounded character like Mario is. If not Mario, then somebody similar who's easy to pick up and fairs well in almost any situation (ask around). Convene with your friend, and instead of trying to play like a pro, take things as slow as you can. Start honing
yourself and not the character you're using. Question yourself as you play. Question your decisions. Question your friend's decisions. Discover the reason behind your actions, behind your opponent's actions. Explore multiple approaches to the same problem. THINK, don't just act. Acquire patience. Discard hesitation. Prioritize your survival.
Prioritize your survival!
...And
practice consistently with intention! As already said, it's the quality of practice, not the quantity. But now maybe you're starting to get an idea of what "quality practice" really is? It's sharpening
you. Not the character you use, and not the tech you learn. You integrate them into your being, not the other way around. And along the way you're going to discover Your Identity - the very thing that will elevate you past this barrier and towards greater heights. Because now you'll truly begin to play the game instead of trying to "game the game."