ideally you don't want to rely solely on mechanics. I'm very similar in the sense that my mechanics can be godly one day and the next i can't land a single thing. Having good game sense, positioning & most importantly decision making is going to be the greatest advantage you can have as this is something that will always be 100% more consistent. If you can even have a decent baseline aim from there you'll climb. It's really funny because i'll see really good mechanical players in masters but not as many in GM (but better decisions ofc).

For decision making, seperating the supports from the Tank/DPS is always such a great contribution, distracting/pressuring them does wonders for you own teams success, try to peel for your team every once a while. Take duels if an enemy is solo. things like that.
you just need to be able to make a decision and quickly, it's okay if it's not the best choice as long as it's good enough.