The Chinese know something about table tennis, and there's a stereotype about Chinese coaches that we can learn from. The stereotype is that in a group training session, they often walk around with their heads down as they do two things - listen to the sound of contact and watch your feet.
They listen to the sound of contact because a good stroke and good timing result in a "good" contact sound. If the sound is wrong, then something else is wrong. By listening to the sound, they can identify there's a problem, and then look to see what the problem is. (So then they do have to look up. You don't want them to look up.)
They watch your feet because the feet are the base of everything else. There's a reason nearly all table tennis drills are footwork drills - many coaches will say all table tennis drills are footwork drills. Get the feet right, and the rest follows somewhat naturally. Get the feet wrong, and all is lost.
So get the sound and feet right, and you won't have to face the fury of all the problems they cause when done improperly. (I'd add one thing to this - if you get both the feet and grip right, often everything in between falls into place. Get either wrong, and everything gets twisted in between.)