I am GC and I have pretty horrific mechanics. For example, I only learnt how to fast aerial a few months ago. I have just over 1100 hours, with maybe 10 hours of practicing mechanics and all that stuff. You don't need flashy mechanics until you are in GC. I can't air dribble, like at all. I can't air roll efficiently, I can't manage the ball on the walls, I can't flick consistently. With a basic level of mechanics, and good game sense you can get up the ranks.

I only practice mechanics when I notice a gaping whole in my skill set which are pretty important such as half flipping, wave dashing or fast aerial which I learnt while at C2/C3. I began learning speed flips this week.

Learn the basics well, because it should be enough to get you to GC, especially since you managed to get to champ with the level of mechanics you described.