I took piano lessons as a kid, and in college launched my music career as a singer-guitarist. But those piano lessons proved valuable later as I moved back to the instrument after realizing that I knew more about piano than guitar. Still, I had miles to go to grow from the fundamentals I’d learned as a kid to what I needed to know to play well enough to perform as a professional, that is, to get paid for playing music.
What I found in taking lessons as an adult was that most musicians, even the most accomplished, take the opportunity to study with someone, at least on occasion. You never outgrow your need to learn more, and you can’t learn something outside your realm of current knowledge unless you work with someone with that knowledge and insight.
Now, you can learn by listening or performing with other musicians. It doesn’t have to be a classroom setting. In fact, listening to music is an important part of learning to play music. It’s part of ear training, which is a key element in any music education program.
It might be as simple as a phrase you like, or a alternative chord or progression that you can pick up from another player. It’s not a case of someone knowing more than you; it’s a case of someone knowing something different, something new to you, or even with a different perspective. No matter how accomplished you become, how well you play, you can always learn something from another player.
If you can find a teacher you like, someone who helps you not only grow in your knowledge but in the joy you get from playing, that is someone you can stick with, whether you see them regularly or occasionally. Getting that kind of input will expand your music vocabulary and provide you more tools to draw on to continuously improve your playing.