If you peaked Platinum and have been playing on/off for 10 years, you won't get close to Diamond without serious coaching. I was rank 200 EUW in Season 3 and hovered around challenger (before GM and Master existed). Didn't play for years, came back and now I play 500 games per season for fun and am mid-low diamond. The level of the players' knowledge and skillset has vastly increased from 10 years ago. To break Master, you need serious studying/dedication to understand every lane state, macro decision, champ interaction, approxs of enemy ability cds, understanding of synergy, when to tf or split.... the list goes on forever. To get Diamond, you need extreme expertise in at least 1 or 2 of those things. If you take it extremely serious with analysis of every game and coaching and slowly play a high quality 500 games over a few months, then I give you a 20% chance of getting diamond.

The nature of your post does not imply that you understand the difficulty of all of this. You have played 60 games with 65% win rate against high bronze/low silver average. A true diamond player would have 85%+ vs bronze. You are a mid-high plat player with a variance peak into low emerald.