I always thought it's more to due to conditioning, athleticism and ability to read the game. Technique is more for ball handling, passing and scoring, no?
Most important element of tackling is timing for me. You have to keep your eye on the ball and pick your time to slide so as to be sure that you can get to it before the strikers foot. Otherwise you would be giving away more fouls (and yellow cards) than winning the ball back, no matter how athletic you are.
Reading the game is slightly different to me. Because, timing aside, sliding into a tackle takes you out of the game for a split second and even if you get to the ball first you could still put your defence at risk. First you decide if tackling is a necessary or viable option. Then athleticism, conditioning and timing help you get to the ball first.
Though it's one of this things that you can only practice while playing the game, unlike for example striking the ball. So I'm not sure technique is the right word for it.