I read about you not improving.
I feel the same way.
Honestly, I don't remember how I improved. I just simply played with people on my friend roster, and I was getting my *** kicked. I changed to Gamecube controller, and it improved my play significantly (not the reason I improved). But eventually I started beating them. I don't know why, I just improved. I also learn new techniques like: You can dash attack with fox, and if you hit them, you can spam Utilt on them. You can also jump in the air, come down, and then do a Dsmash. Honestly, those can be really predictable, but it's a start.
I don't remember how you played when I last fought you, but, you probably need to work on spacing. Try not to get so close to people when you attack. Some of the fast attacks I like to use the most. I rarely use a dash attack. I like to run up and do an aerial attack. Like with Marths Fair, or Toon Links Nair, or ROB's Nair.
I just figured out what I needed to improve on. I learned how to shield when someone came at me and attacks me, and then I grabbed them. It took me 2 years I think to get this good. Maybe less, I don't know. I just kept playing until I eventually improved. I only improve in general aspects of the game, like spacing, reading, and other stuff maybe.
Now, at my level, improving is so hard. @_@ I don't know what to do. Xiroey told me to not force it.
Oh and another thing, when spacing with Meta Knight, let's say you wanted to attack from above with a Dair. You don't want to fall down on them and Dair, which you will then fall right next to them. If they block it, you're screwed, and you'll get grabbed. As for Meta's Fair, you'll just have to try to space that as good as you can. Eventually you'll learn how people play, and you'll be able to make better decisions more accurately when you play. You won't know what to do to improve, maybe. It's frustrating to try to improve, I get so frustrated when I am trying to improve and games. I feel like I can't, just like I am with brawl now. I'm struggling.
LOL, TL;DR! (Too long; don't read) But seriously, read it. xD That's just what you say when you write a big wall of text.