I'm 51 and I plan to learn guitar this year. I sing and play a bit of percussion. Just because it might be harder for us to learn new things doesn't mean we shouldn't. I took me many years to learn to sing well and I had to put in 1000's of hours, and I don't expect it to be different learning guitar. I've learnt a few chords in the past.
Also I am teaching myself to draw and paint and I'm 51. I did a few classes in painting and bought myself a "zentangle" how-to book to get started, because, like you
@Markness, I felt too intimidated. Zentangling is a good approach for people like us, who are scared and really hard on ourselves and who have copped a lot of discouragement.
I don't think there is a "too old" to do art or music. You just have to learn to ignore that judgey inner critic voice, while you are getting started, because one can't expect to be good prior to a lot of practice; a lot of doing is required to learn to be "good". In other words, we have to be OK with sucking, before we can be "good" in our own eyes. I didn't like my singing for the first few years, maybe even 10 years of singing, before I started to think I was pretty good and I liked my own singing voice. I still think I'm not good at visual art, but, I want to get good so I'm going to persist. And I'm going to be not good at guitar for however long it takes to get good.
But any art form is very personal and there is a strong degree of subjectivity involved. Personally I like authentic, emotional music more than technically perfect music, and I like art that shows the unique perspective and personality of the artist more than technically or commercially popular so called "successful" art.
It's more about expressing yourself than conforming to anyone else's expectations or preconceived notions of what people might think is good or not good. Be creative to please yourself, more than anyone else, and if you learn to derive some pleasure out of it, other people are sure to pick up on that and enjoy it alongside you, too.