These choices are trade-offs. If you want to write a quiet song, it won't be loud. If you are writing a software tool and you want to prioritize speed over simplicity, then it won't be as simple as if you'd prioritized simplicity over speed.

There are two main signs that you've succeeded at your goals. The first, and more pleasant, is that you get compliments about how your thing is like you wanted it to be. "I love that song, it's so quiet!" "Your tool is so fast!" Why thank you, that's exactly what I was going for.

The second sign, though, is that you will get complaints. Specifically, people will complain that your thing does not achieve the things you didn't set out to achieve. "I wish this song was louder", "this tool is so hard to use". That you are receiving complaints at all means that people are aware of your creation; that they are complaining about what you specifically set out to make a non-goal is a side-effect of the fact that you made that trade-off.