During my years of coaching, the #1 question that players ask is in regard to the correct racket angle when looping.  Having the correct racket angle for each particular stroke is important.  However, there are many many many factors that need to be calculated within a split second to adjust your racket angle to properly loop the ball.
 
#1 The height of the incoming ball
#2 The depth of the incoming ball
#3 The speed of the incoming ball
#4 The type and amount of spin on the incoming ball
#5 The trajectory of the incoming ball
#6 Your body position
#7 Your racket height
#8 Your backswing
#9 Your amount of tension in your arm
#10 Your amount of racket speed
#11 The desired height of your loop
#12 The desired depth of your loop
#13 The desired speed of your loop
#14 The desired amount and type of spin on your loop
#15 The desired trajectory of your loop
#16 The type of rubber that you are using (inverted, pips, etc..)
#17 The amount of grip on the rubber you are using (slick, somewhat grippy, or tacky)
 
To make 17 calculations and adjust your racket angle within a matter of ½ second take a lot of practice.  No wonder the top players practice 6-8 hour per day for years and years to reach a high level.  Table tennis is way too fast to make 17 conscious calculations prior to each hit.  The mind needs to be properly programmed to look for those signs and make fast adjustments.  Getting a good coach and learning properly from the start will be the biggest benefit to developing the foundation for your game.