As I've had a few enquires from adults keen to learn something new after the restrictions lift, I thought I'd address a common worry from potential adult students. The answer to this is "no, you can never be too old!" In fact there are a few advantages that adults have over children when it comes to learning an instrument. I'll go over the main two that I've noticed in my teaching experience.
1. Focus and attention to detail. Adults are better at being focused and can keep their concentration for longer which helps as playing music requires reading, counting, technical ability and expressiveness. Adults also protect their practice time as they understand that getting good results depends on how much practice they do.
2. Having life experience means that adults can interpret what they are playing into meaningful expression. This means that for them playing music is a stress reliever and are more likely to practice.
This is not to say that children are incapable of concentration or that they can't learn how to play their instrument with emotion; I have some wonderful students who are very young. All it means is that they need to be reminded to do these things by their parents and teacher.
If you are an adult wishing to learn an instrument there is nothing stopping you! :-)