You're never too old to learn. At age 71, I was concerned about difficulties I was having with my voice. Having sung in a choir for 40 years it was devastating to think I'd no longer have the joy of singing. A hearing check and music lessons were recommended at a workshop for the so called aging voice. Weekly sessions recommended by Erica have solved my problem. Now I am well past 71 enjoying singing as much as ever and doing better that ever. Thanks Erica!
Singing in tune is a difficult thing. It requires 1) a technique that allows you the comfort and flexibility to adjust your pitches quickly and freely and 2) a constant awareness of everything around you and 3) knowing what to listen for.
As singers, we may have days when we are physically compromised and are struggling with technique, then we have words to deal with sometimes in a foreign language words that we have to pronounce correctly and interpret. We also have our facial expression and in the case of an opera or musical or actions and or dancing.
Being nervous can add another complication. It is a lot to juggle and a lot of elements fighting for our attention. All of it is important, however the one that will be noticed the most will be the tuning. It doesn't matter how big your voice is or how lovely the tone or how well you act, if you sing out of tune it isn't pleasant to listen to and will even give the listener the impression that your voice is not that beautiful.
There is a simple test you can take to see if you are too old for voice lesssons? Take the first two fingers of your right hand and place it on the inside part of your wrist of your left hand. Do you feel anything? If so, you are not too old to take lessons.
You may not be able to sing the part of "Annie" (unless you are naturally very short) but there is no reason why you can't learn to sing and to sing well. There is also no reason why you can't perform in public in choir or on your own if you want to.
There are also many physical benefits of singing. It will keep your speaking voice young. Just like any muscle the voice deteriorates through lack of proper use. It can also deteriorate through misuse which is even more reason to take lessons.