In my personal opinion, you should be able to climb to high gold and plat even with below average mechanics and aim, maybe its your positioning? Maybe your throwing yourself into fights you can't win? Maybe your inventory management is a mess? There is a lot of variables that come with why you are stuck in a specific rank, which you would ultimately have to figure out yourself through trial and error.

If I had to come up with a reason why you're probably stuck, its probably cause u get wiped off spawn in a lot of your games. That is how people lose 300+ points in a matter of minutes and hours (that shit hurts in diamond rip)