You are never too old to learn.
The capacity for learning does not expire.
What They Mean
Enroll anyway. The mind accepts new material at any age, and the deadline you are worried about does not exist.
Are They Right?
Yes, with modest administrative notes. Learning continues throughout life; it merely prefers a quieter room and a better chair than it used to.
What They Left Out
You are occasionally too tired to learn, which the saying treats as a scheduling issue.
They Also Say
Read the ruling: You Are Never Too Old to Learn vs. You Cannot Teach an Old Dog New Tricks