Right now I can only go online and learn how to play songs, and with practice I can play the song eventually, but when I learn how to play another song, I don't feel any better. What is the essence of being a good guitarist? knowing how to solo? the techniques? in which way should I proceed to truly get better at guitar? learn to play some classical perhaps?
The essence of a good guitarist is:
1. Learning every inch of the fretboard and strings. Knowing what to do with your left And Right hand to get exactly the sound you want.
2. The ability to make any song your own. Most journeyman guitarists can copy someone else's style. There are whole libraries devoted to books on how to sound just like Eddie Van Halen, or how to recreate every note of the main solo in Stairway to Heaven. I used to play Stairway to Heaven as a Bossa Nova instrumental. Bluegrass groups do a version of stairway to heaven that the average fan might not even recognize. There is so much more to a song than being able to create a taped version of it live.
3. Learn to appreciate music from your past. I don't just mean the sixties here. Figure out for yourself why Ritchie Blackmore thinks it's more interesting to work with a group that plays medieval and Renaissance music instead of being content to make millions reliving his glory days chunking out the intro riff to "Smoke on the Water" one more time! Figure out why Kemp's Jig can be just as much fun to play as Crazy Train.
4. Learn to express yourself in the language of altered chords. Discover polyrhythms. Explore the uncharted waters of Jazz, Fusion, and Latin music. Learn the intricacies of Flamenco. Create your own style of music! What are they doing with a guitar around the world, that you've never heard of? Have you tried the Russian discipline of seven string guitar? Have you played with modal tunings? Can you put down the plectrum (pick) and play fingerstyle?
5. Learn the history of the players you admire, and discover what drove them to do what they did with the guitar. Study the Blues pioneers like Son House, Muddy Waters, Lightning Hopkins, Josh White, and Robert Johnson. Get hold of those scratchy old 78 recordings and find out why guitarists spend days listening to them over and over again, finally recording them on cassettes because they are afraid the shellac is going to wear out before they "get" that one last lick down. Learn the history of the players you may not know about yet. Check out master world guitarists like Michael Chapdelaine and Stefan Shyga and find out why they are teaching instead of just performing.
I hope I have given you some grist for your mill and set you on the path. If you feel like you have strayed or come to the next crossroads, give me a shout. I'll be glad to try and help.