Post replays on your character's discussion board, and the right people will tell you what you're doing wrong.
You really don't earn my sympathies unless you've actually tried every available outlet to improve, and a "How do I not suck" thread is a less than half-assed attempt at doing that while simultaneously trying to justify your feelings from losing so much in For Glory.
You see, people quit playing Smash likely very frequently due to a lack of confidence in their ability to improve, or being defeated consistently hurting them personally. Online play only speeds this process up, because instead of only infrequent tournament days you get to play with real folks, you can play against other people at any moment.
Seeing as how you say you have been playing since 2008 "competitively" and haven't yet bothered to go to an actual tournament (the only way to actually improve past being average), it's clear that you've yet to actually put any effort in to improving despite what you say. Getting your butt-kicked in For Glory is necessary at this point, because it is due justice to you for believing that you can land anywhere on top practicing for years purely on CPU opponents. A swift reminder that Smash is actually a multiplayer game and in practice, requires another body to have a "real" match.
If you don't want to do any of this, then you don't deserve to improve. You have not done everything you can and you simply want a free pass to wins because you have spare time to play Smash by yourself, and in this case, I say quit trying to call yourself competitive and find fun in Smash's admittedly amazing casual aspects. If you can't do that? Quit period.