I want to learn. I want to study. I want to improve. But I legitimately cannot for the life of me figure out what it is that I'm doing wrong. I want to know so I can change it, but it just isn't working. I watch my replays, I pay close attention in game, I think and think and think. I watch videos, I read guides. But the stuff I'm doing seems to be "right", but when I try it, it just doesn't work. I practice and practice, both online and in practice mode, but when I face a serious opponent they run circles around me and I don't understand how or why.
I would love any kind of help. Practice, advice, videos, anything. I just want to improve. I don't really know who I main, I mostly play Zard, Palutena and Robin but I don't especially like any of them. I've tried every character but I haven't found one that feels really right to me yet. Still looking.
Best way to start is here. It's a good thing you actually want to improve, most people I try to help in real life don't want to, and they get nowhere.
I would like to point out that all the mains that you have chosen in your original post are characters with strict learning curves.
I would know since I main Palutena and used to main Robin. I went on and off with Palutena and completely acknowledged her the worst character in the game, until I started messing around, now I can beat all my friends with all my stocks remaining. Point is, I didn't get this far by just giving up on Palutena (which, mind you, I was THAT close to doing). Palutenas not going to be an easy character to learn, and if you're having trouble learning the basic mechanics of the game, I suggest to either mass train as her, or get used to another character to better learn tricks in the game, then get back to her later (which is actually what I did). I know its a bit crude to say that, but she has one of the hardest learning curves in the game. First I played Robin, I found his running speed too slow and his attacks too situational... winding the clock further in the future, I was wrecking online.
How did I get better? I did a couple of things:
-Go on the Replay Channel, set it on the character I want with the option of 1v1 only, and see if I can see some new tricks
-Read some character boards at Smashboards (sadly this doesn't work with all characters in my experience)
-Mess around with the character
-See what I could do and not do that felt natural: If moves don't come naturally, there is something wrong
-Take a break from the game
-Switch versions (Wii U, 3DS) and controllers
-Play with humans
Also, saving and rewatching replays is a good idea to reflect on your mistakes. Also form things like "mini-strategies" (as I like to call 'em, or I guess combos will work, and be a better word for it, I have no clue at this point) in your head, like if x happens, I should do y. You mentioned this before when you said: "I hit him with Arcfire and try to go for a SH LSFair" x being if Arcfire hits, and y being following it up with SH LSFair. I do something similar with ZSS too, if DSmash hits, I should do FSmash. These should come naturally.
Maybe pointing out some things you messed up on will help?
I am Robin, my opponent is Charizard. I hit him with Arcfire and try to go for a SH LSFair, but he jumps out of the Arcfire just before I can hit him. When I see this maneuver in videos and on streams it works every time. Later on, I play as Charizard and my opponent is Robin. I get hit by Arcfire and mash jump as fast as I can, but Robin hits me with two SH LSFairs.
Arcfire + SH Fair would be a good combination, especially with a big character like Charizard. However, if you have had no practice with executing that, you're probably going to miss. If the game even has slight lag, there is a high probability of messing up. Alternatively, he could have escaped it early, he could have not been directly in the middle of it, or you could have waited too long to execute it. The second time there might have been a really experienced Robin, or less lag.
I am Palutena, my opponent is Marth. We run towards each other, Marth stops to shield. I do a dash grab from close up. I slide completely through Marth and do not grab him. I bear the full ending lag of my dash grab, which is about 1 second. Later on, we run at each other and I stop and shield. Marth does a dash grab from approximately the same range. I am grabbed.
Palutenas dash grab is something to take note of, you're better off keeping some distance from your opponent and grabbing, rather than being right next to them. Alternatively, if you WANT to be right next to them to grab, use R+A to grab (make sure that shield is put up first, with good timing, you can do this on the first frames).
I am Robin, my opponent is Falco. Falco uses Dair and I dodge it. Since I know Falco's Dair has some landing lag, I try to snipe him with Thoron to punish. He manages to spot dodge it. Later on, I miss a Fair and Falco charges a smash. I try to spot dodge it but the spot dodge does not come out and I die.
Thoron has really bad startup lag, this shouldn't even be considered to be a move to punish for anything. Even a Pit's ending lag for Side Special for example could escape that. Robins aerials have a lot of ending lag, Falcos smash attacks usually don't.
I am Mario, my opponent is Charizard. I Utilt him twice but he DIs away and I cannot combo him. Later on, I play as Charizard vs a Mario. He utilts me and is able to utilt me about 15 more times into a killing usmash and I am not able to DI, air dodge, or jump.
This is more of a thing of positioning, timing, and knowing how to pull off DI. A Toon Link Utilted me up to 80% (from 0%) because a platform you can't cross through was right above me. A similar thing may have happened here. Alternatively, lag could have been messing up inputs.
I am Robin, my opponent is Sonic. Sonic rolls from behind me to in front of me, so I know I can punish. I throw out an ftilt just after he recovers. As I ftilt he uses grab. The ftilt visibly clinks against his grab hitbox and I am grabbed. He takes no damage or knockback.
I have nothing to say rather than, that's some unlucky timing. It happens, and has been a game maker or breaker to me before.
I am Robin, my opponent is Sonic. Sonic does his Side-B towards me and when he is in melee range I fire Elthunder. Robin says "Elthunder" and the projectile seems to leave her hand, but Sonic is not damaged and takes no knockback. Instead I am knocked back by Sonic.
I'm not entirely sure about Sonic and his Side B, however, it may have either had: Super Armor(?), Priority(?), or he was too low on the ground for it to hit. Alternatively, he may have cancelled your Elthunder.
Even really really simple stuff. For example I get juggled a ton because when I try to air dodge my opponents' juggles the air dodge never comes out in time, or I get hit while the air dodge animation is still playing even. This results in me losing tons of matches where I have an enormous lead.
This is the kind of thing I mean. I do not understand why I can't get these to work. I know what they are and how to do them, and in practice mode it looks like I do them the right way. But against humans they always fail, inevitably. And I always lose. I cannot understand how this is happening. I am trying to play more safe, to not make moves that are punished so easily. But in particular, I am never ever ever able to time my spot dodge the right way. I can do it perfectly every time against a level 9 bot, but against a person I miss every single one. It leads to me getting grabbed an awful lot.
Referring to the bolded sections, NEVER play with Level 9 AI. They are absolutely the worst to train with. I tell people that training with AI is bad, because one you understand the patterns for them, you'll start applying them to human characters which never play like Level 9 CPU. Also, level 9 AI literally read your inputs and counter them, humans cannot (I mean, they can "read" opponents, but they can't know what button you are pressing at the exact time), so at least try with Level 8 CPU if you have no options. Alternatively, it may just be lag that is messing up your dodge inputs.
I've been doing some note-taking on separate characters and writing down things that work and don't, perhaps this can help you, and you can use these to help others.
Anyways, best of luck, I really do hope you continue to try and improve, and if you have any questions, you can ask me or any of us, really.
EDIT:
If you want a well-rounded character, pick Dr. Mario (he's better than normal Mario in my opinion)
If you're not good at dodging, pick Bowser or Ganondorf. They can take a hit.
If you spend most of your time in the air, pick Jigglypuff or Meta Knight.
If you want a simple, fast character, pick Sheik or Fox.
If you want a character that controls fluently, pick Wii Fit Trainer or Zero Suit Samus.
IMPORTANT. Just wanted to leave this here.
