It's very important to point out a very simple fact: Flawless playing doesn't exist by definition, simply because music is a continuation and expression of a human, and since there is no such a perfect human being, there is no such thing as perfect music.
There's no such thing as a proper and improper tone production. There's no such thing as proper and improper hand placement, rubato, or expression. Approaching music with any sort of idea what's "proper" and what isn't is just stupid.
For any musician tone production, hand placement, and technique are only tools that he uses to express himself. Everyone has a different way of applying those tools, because every person is unique, and therefore every single person's music is unique. If a musician is fully opening himself up through his music, then his playing is sounding exactly the way he wants it to sound, and when that's the case, it's stupid to look at his hands and think that his hand placement is off, or that his tone production is improper, etc. You can only say that you like or that you dislike the music that's coming out of him. Maybe you don't like it, but someone else might. That's normal.
First and foremost, you have to consider as a musician solely as a person, with all his flaws and shortcomings. In the same way that we can like or dislike a person, we can like or dislike his music, but just because we dislike him doesn't mean that he's a bad person and a bad musician.
If a musician ideally expressed himself as a person in his music and it sounds exactly the way that he wants it to, then that musician a master of his craft.
Your goals always define your tools, never the other way around.