Focus on other aspects of your game. Potentially all of the following could help you out:
- Aim practice / modifying your technique.
- Movement / Dodging / Jumping / Role-outs.
- Map strategy / locations / timings / positioning.
- Game mechanic research / weapon & fall damage.
- Opponent player & team research.
A lot of people focus entirely on aim because it's the most highly sought-after skill as it is the easiest to see noticeable improvements in. The thing is, making yourself harder to hit could mean you get an extra free shot on your opponent which allows you to miss one of your own shots and still get the same result. Getting into positions quicker or more efficiently could result in a completely different outcome regardless of death match ability. It could be the different between you picking up an extra health pack before you fight, or getting to your medic faster resulting in a larger overheal before you're forced to enter combat.
Learning map timings is important. Sometimes you can predict (with a high degree of certainty) where a player is based on where he is not, because if he was coming that way he would have been there by now (hope that made sense). Also thinking about your positioning and advantageous map positions and then actively using that knowledge in combat to your advantage. It might sound like something you only learn once, but the more you spend time thinking about it, the more you will find yourself using it.
In a game like league of legends, professional players rarely enter into fights that are 50-50. Both players know in advance that either they will win the fight, or lose it based on their kit, their opponents kit and a number of other factors. Sometimes you see a player with barely any health left, still continue to fight and win when anyone else would have ran away. That's just game knowledge. Knowing if they dodged that one skill, they would have enough to survive and could deal out X amount of damage back at the enemy. You're never going to know exactly how much you can do, or how much health the enemy player has, but it helps to know that 'I could survive 2 rockets as long as I keep roughly _this_ distance from the soldier but if I go any closer I will die in a single hit'. Again, actively practicing this does help your main game.
Player research is a big one, especially if you find yourself playing against the same teams and players all the time. Some players only ever take a single route to middle and get there at exactly the same time every game. If you watch a couple of games and find one of these, maybe your demoman can land a completely blind, long distance sticky on them with just a little timing practice. Maybe as a soldier you can prefire players. Maybe a scout has a certain jumping pattern, always going left then right in the air but never the same direction. How good you are at the game is directly proportional to the competition you are playing against, so by reducing the effectiveness of your competition, your 'level' increases.
So yeah, you might find that one aspect of your game has hit a wall, but there's always more you can do to improve. It may look pointless on paper, but some of these things DO win games.