You're right. You can't determine whether or not someone is bad based on their record. But you can determine their skill based on how poorly they make use of vision. Warding means jack shit when your team doesn't use that vision. If you get caught and you could have escaped consistently then you are unskilled. If you die trying to take inhib and fail because you weren't paying attention to the enemy death timers you are unskilled. Seriously I started playing long before trinkets, buff timers and death timers were made a thing( death timers you had to tab to see, but not the point). These resources were included for a reason and not using them is being bad.
Regardless of win or loss records if you do not use these to make decisions you are either being carried or feeding. Probably both.
Now granted ppl make mistakes, but consistently making these mistakes is a great indicator that you belong in Wood 5