Absolutely! You can improve your game without a coach by taking advantage of the many free and paid resources available — books, training videos, online courses, and forums where you can discuss hands and strategies with other players. Consistently studying and reviewing your own hands is one of the best ways to grow as a player, especially if you're honest about your mistakes and actively seek to learn from them.
That said, having a coach can speed up the process and help you identify leaks more efficiently. But if you’re motivated and disciplined, self-study can take you a long way. Many strong players started out without coaches — they just put in the time, stayed curious, and kept learning.