Is Playing Good Practice
There are three things you need to do over time to really improve your game. The first is to take lessons. Without a focused look from an expert on what you are doing wrong, you will always struggle to improve. It is amazing what we don't know about our own game!
Next you need to practice what you learned. It does no good to know something, but not be able to do it consistently. The big problem I see here is players practicing incorrect things or not practicing in an organized fashion.
The final piece to this improvement path is competition. Whether you match up for money or play in tournaments or leagues, testing your knowledge and skill is a prerequisite for improving. Without the added pressure of playing to win, you miss out on the mental focus required to improve.
Then after your competition, you go back to your instructor with your problems and lessons learned. Your instructor will give you more new things to practice. You do the work and then go back into the arena.
Over time if you follow this path, you will improve tremendously.
What I see a lot of players do is skip the instruction part for a lot of reasons. Then they wind up practicing bad fundamentals etc, and are frustrated with their pool game, don't know why and seek answers in all the wrong places. Many players look for answers in more money games, more practice, a new stick, etc. Unfortunately they are missing out on a big piece of the improvement formula. You really need an educated outside set of eyes to help you see how you are really playing.
This is not magic, but it works in football, baseball and other professional sports.