How much does does KDA really matter?

So I just played a top lane game where I went 2/1/3 with 170 CS in 25 minutes, along with taking two towers, winning my lane easily. We also won the game, but I felt like I didn't have a good game, even though I farmed well and didn't feed. However I also saw that I got an A grade after the game (which was probably the farm), and I was wondering how important KDA really is if you don't feed and you farm well, especially when playing a lane that is as isolated as top. I feel like in some cases the importance of KDA is exaggerated, but at the same time isn't it easier to win games with more kills? An example of what I'm saying is if the top laner has a similar stat line as stated above in the same amount of time, and let's say the mid laner goes something like 12/8/3 with around 120 CS, how much more important would that mid laner have been to winning than the top laner, even as the top laner was taking objectives and farming?