How can I improve for champ as a low tier diamond? (PC)

My highest elo was emerald 3 like two years ago. I started playing consistently again and now I’m at diamond 4. I’d say my aim is alright 53.3 HS% with a 1.1kd. My game sense and map knowledge are above average I’d say, yet, I’m very inconsistent on whether I play really good or bad/mid. I mainly solo queue but when I stack with diamonds/ champs from the siege discord it’s 50/50. I think it’s due to my mental from seeing high ranks idk.

I’m just looking for tips on how to improve. Any advice is appreciated. Thanks.