Can one be too old to learn an instrument?

I own a guitar. I've owned it since I was about 13, but never really got into it because I was a spiteful teen who wanted to play the drums, and went out of my way to play the drums instead (to the dismay of my parents who acquired the guitar for me).

Now, as a 22 year old, I occasionally find myself entertaining the thought of picking it up and learning it. I really would someday like to learn music theory; I have created digital compositions for awhile, but struggle with keyboard and string derived instruments due to not knowing even basic music theory.

It takes me a very long time to derive melodies as a result, and I am hoping that learning a string instrument would help me develop the skills to be a better composer.

I mentioned this to one of my colleagues in the music industry, and while he was supportive, he warned me that I may have trouble seeing as I have never really picked up the guitar and that this is an older age to begin learning it.

This really discouraged me. If this is true, what limitations can I expect in the way of learning? I already have a lot of trouble playing due to the size of my hands, and hearing this is making me wonder if I should consider a different instrument entirely.

To be clear, I am asking about both the fundamental theory and the physical technique, as I have no formal education in other.