By playing worse people = you make them better
By playing better people = you get better
Therefore: If you play worse people, and make them better. Then you're eventually playing better people than you were. Making you better. The key is, to not just play with the same people, continuously. Play people better than you at tournements, improve yourself, then improve the worse people. Eventually they'll be able to go to tournaments and play better people at tournaments, and get better themselves. So when you play those worse players, they'll be better again. Making an endless cycle to everyone getting better.
There are three things that make up a competitive Smash player (or any one competitive for that matter): Skill, knowledge, and creativity.
Skill - The ability to perform a task/move/combo. The more skill you have, the more efficient you become with that task.
Knowledge - The ability to know things. lol. The more knowledge you have, of anything and everything, the more efficient you become knowing what to do when.
Creativity - The ability to not become repetitive. The more creativity you have, the more efficient you become at adding variety to your game (often referred to as "mindgames"), learning, and winning.