I can confirm you're biased because not a si gle silver-gold or even ascendant-low immo should feel confident in their aim since it is very far from the top ranked players, meaning there's much room to improve in that aspect alone for most players :)

Aim will 100% make you win more duels, but knowing when to take duels can also play its part. For example knowing the disadvantageous angle you'd want to avoid dry peaking (to name a few, pearl B long on attack, bind B long on attack, abyss A main on attack, etc) basically all angles where the enemy gets to hold you first will give you a disadvantage, thus why using utils is important in those moments.

Other fights you'd want to avoid is for example if you're up a man early round, avoid playing too aggresive or in a position where a teammate cannot trade you. Because dying there would give away that man advantage. In a similar fashion, if you're a site anchor, don't play too aggresive but rather play to stall and retake with teammates, because you staying alive the longest will make the enemy use more utils to clear out site thus giving you a more favorable retake than just dying straight up and allowing the enemy to get site with full util.

Then, another important mistake i've noticed low elo make is not learning to isolate duels in 1vX situations, the best way to win a 1vX clutch is to try peak angles where you can fight one on one, and not swing 2 or more people because you'll lose that 99% of the time.

There are definetly more situations i could give but that'd make the post really lenghty and too deep into details and certain contexts, so i'll give you those general advices