When my mother first purchased a billiards table for a $1,000 I thought it was a waste of money. My mother made me play it and despite my dislike of the game I gradually got better. The power of practice is well known. If you practice you will get better but it has to be applied practice. Some say perfect practice makes perfect, I say progressively perfect practice makes perfect.
That's why you have to approach a game like billiards as learning one shot at a time. When you first play billiards, you have a hard time making easy shots. Your first goal becomes to avoid hitting the white ball into one of the pockets. You gradually gain control of the stick.
The next thing that happens is that you start making the easy shots. You start learning what shots just won't work. You begin to memorize what will happen when you hit the ball a certain way. Some people think of billiards as a game of physics. I think of billiards as a game of memory. You play the game enough until you memorize exactly what will happen to the balls as you hit the white ball with a certain amount of force at a certain position on the ball.
You don't need physics to predict what will happen, you need prior experiences to infer what will happen. Like all sports, physical attributes matter. The longer your legs are and the longer your arms the more options you'll have in making certain certain shots. Physical attributes also largely render physics calculations irrelevant because differing physical attributes amongst individuals confound simple calculations.
Subtle things like how you hold the cue or your stance also confound physics calculations. These are only things that can be observed by practice and the effects of these individual eccentrecities can only be experimented on with practice. If you want to learn how to play billiards, first start with simple goals like drilling easy one ball shots. Then work your way to two ball shots.
There are tons of potential one ball shot variations. Just keep drilling those shots and keep experimenting with what happens and you will get better at billiards.