Technique doesn't come from a finger exercise. It comes from knowledge of physics, anatomy and mechanics. Your arm is a "machine" of levers, pulleys, rubber bands, fulcrum and there are proper and improper ways to move. Hanon nor Czerny can give you that. No matter how many hours and decades you spend playing them, if you are moving incorrectly, you are only hard wiring improper movement into your brain.
Learn to move properly and a facile technique will just fall out of your hands with no exercise, warmup or need to practice. Do you need to practice riding a bike? No, once your brain hard wires proper movement and balance, it is there forever. The arms are no different. Once a bad habit is hard wired, like the first time we touch a piano, it can take a lifetime to eradicate it.
If you learn to use the incorrect muscles as most pianists do, or non-existent ones as Hanon and Czerny espouse, you will hard wire improper movement into your brain and forever struggle to beat your hands into submission. That is why teachers spew "endurance and strength" because they don't know the laws of physics which result in effortlessness.
If you've ever run in a three legged race, at first it is a struggle but once you and your partner sync up, it is easy. However, if one of you doesn't have the mental acuity to sync, there will be an imbalance and there is not much YOU can do about it.
Playing from the wrong muscles creates a myriad of imbalances and teachers think you need "strength and endurance and more practice" to fix it. No, you need a better teacher.
Playing the piano is all in the arms. The fingers are the conduit between the brain and piano. Hanon can be wonderful if you have an ergonomic technique but, if you have an ergonomic technique, you don't need Hanon.
If I see Hanon at a garage sale for a nickel or quarter, I buy it so no one else does. Then I use it to start the fire in my smoker. Mmmmm, 16th note burgers. Gurgle, drool . . . . (my Homer Simpson impersonation).
If your teacher doesn't know how the abductors affect the flexors or, the importance of pronator and supinator muscles, or the dangers or ulnar and radial deviation, then you've probably already developed bad habits.
Likewise, if a teacher teaches to cross the thumb under the palm . . . RUN!!!!!