Often a player has trouble with something very specific, and yet only practices against it in actual games, where he only sees it now and then. This allows little chance of any type of systematic practice to develop the proper technique. The same player probably did lots of systematic practice to develop his main strokes – forehands, backhands, looping, serves, and so on. And yet, he doesn’t apply this to other aspects of his game.
For example, if you have trouble with a specific serve, it should be your quest to find someone – a coach, top player, or practice partner – to do that serve against you over and Over and OVER until you are so proficient against it you never have trouble with it again.
If you have trouble attacking heavy backspin, the same applies. Perhaps have someone feed heavy backspin in multiball so you can systematically work on your technique. Or do a drill where you serve backspin, partner pushes back heavy, and you attack. You’d want to do both of these, the multiball ball for more systematic practice, the latter because it’s more game-like.
If you have trouble blocking spinny loops, such as the ones you get when you push with heavy backspin, then have someone serve and loop against your push as a systematic drill. In fact, to maximize practice, get a box of balls and don’t even play the point out – partner serves backspin, you push, partner loops, you block, and as you do so your partner is already grabbing the next ball.
If you have a specific weakness against something, work out a drill so you can systematically practice against it until it is no longer a weakness. Or just play games, have fun, and spend the rest of your table tennis career with a fixable weakness that you’ve chosen not to fix.