Being able to play 15-20 chords .....is just the baby steps of knowing how to play the guitar.
Have you seen those classical guitarists with competent skills but can't play anything else without the music scores in front of them, I lived with one for close to 20 years, that person was me. What I did was an exercise in muscle memory trainings, nothing else. Can I play the guitar, the answer yes. Can I play music on the guitar? The answer is a big fat NO!
On the same token, have you seen guys at guitar shops, playing impressive riffs only to find out that's the only thing they know how to play. Again these people acquired the skill through muscle memory training, but can they play music, I believe the answer is NO.
There was this old man in church that used to play electric guitar during the prayer meetings, now this guy can accompany just about anyone in any keys. There was no fixed lead singer for the group so songs would invariably be sung in different keys from the previous weeks. No sweat, the old man will just move the keys around on the finger board to suit the singers. Now that's what I call knowing how to play the guitar.
Learning to start to play the guitar may take a few weeks, but mastering the instruments as in knowing how to play music on the guitar takes a life time. I am still on that journey and I hope that everyone else who loves this wonderful instrument will continue their journey of discovery.