Having a good mice does help indeed, but not by so much. In my opinion a mouse that perfectly fits you is what you need, then the skill only comes with other adjustments.
A good mice is :
- A good shape (fitting to your hands depending on how you grab a mouse aka palm grip, claw grip, fingertip grip or 131)
- Good sensor
- Lightweight if possible (mices are getting lighter and lighter these days since glorious came out with their sick Glorious model O that worth only 50$, but weight depends on you too.)
- Good cable or no cable if possible
But again you really need to know that a good mouse fitting your hands is what you need, you won't instantly become better using a new mouse that fits you more than the previous one, but it'll be easier indeed to improve using a good product that you feel comfortable with.
I own many mices and now I just switch between all the mices I got because I can't seem to have a real fitting mouse, but that's a lefthander problem so anyways.
Also you should never ever focus your whole time on "aim" purpose, being good is having a good aim, but also moving around maps using your brain, using the environement to your advantage etc...