You have not maxed out what you can learn by yourself, if you just get a little motivated. Lessons are great. Playing with other people is always good. But even on your own, if you have a computer and an internet connection, you have all you need.
One of the most important lessons I got was from a chat with Janek Gwizdala, when I asked him what was the most important and beneficial thing I could work on. He said "transcribe everything".
I took that to heart, and I've learned a LOT from it. Learn basslines and solos note-for-note, including every fill, and the exact phrasing and feel. Do this for every style you can get your hands on, and find things that are challenging and interesting for YOU. James Jamerson, Paul McCartney, Dream Theater, Mahavishnu Orchestra, Ray Brown, Lynyrd Skynyrd, Victor Wooten, King Crimson, Tribal Tech, Kansas, Yes, Weather Report, Marcus Miller, Screaming Headless Torsos, The Who, Rush, Bob Marley, Brothers Johnson, The Dregs ...
Learn one tune in a different style a week PERFECTLY, note-for-note, and your playing and your ear will grow more than you can imagine.