Ofcourse you can, but you can always check the new meta cuz sometimes its better on your champ than the previous ones mby debuff some of your stats but also buff others
leveling up in lol is a mix of luck along with good gameplay, it's not enough to be good at the game if you're unlucky some days we lose more than we win and others we win more
of course you can especially if you're using scripts, vayne top will always be strong with scripts same with vayne or jinx botlane even when adcs are a bit weak same with cassiopeia yass or yone mid. main thing is stick to a champ max 3 champs so you understand when to engage and your limits
Certainly, you can improve by focusing on both macro and micro gaming aspects and mastering two champions you enjoy playing. Achieving proficient farming is crucial for becoming stronger, and it's worth noting that many non-meta, monochampion players have reached the ranks of master or grandmaster.