Many people don't learn Greek because their textbook is too complicated. If something is too complicated, you're not going to do it. Learning to read New Testament Greek doesn't need to be complicated in order to be effective. You just need to know exactly what you need to do. You need to know what is essential and what is not. You need to know what you don't need to know. You must ruthlessly eliminate all those things that aren't essential for you to learn Greek. The payoff isn't worth your time or effort. Resist the temptation to keep adding more textbooks to your bookshelf. That's not going to get you the results you want. In fact, it's going to drag down your willpower and focus.
Find a simple textbook and stick with it. Success will follow.