I don't want to put the user on blast but I just saw a "you're never too old to start" post about the Artemis II astronauts, and, respectfully, they are astronauts on our first trip back to the moon since Apollo because their entire lives have been building up to it. Christina, the youngest on the crew, wanted to be an astronaut since childhood, has two bachelor's degrees, and has been involved with NASA since 2001, well before she joined as an astronaut. Jeremy joined the Canadian equivalent to Civil Air Patrol at 12 and did his undergrad in space science. Reid started out as a Navy pilot in the late 1990s. Victor went to a public Ivy, has three master's degrees, and became a Navy test pilot 20 years ago. These people's whole lives have been building up to this.
We are not yet at the point in human space travel where you can just up and career change to being a working astronaut* unless you already are very well-established in a closely relevant career (like medicine), or you're part of a specialty program training mission specialists (like Christa McAuliffe was).
*as opposed to a space tourist
Perhaps a better message, if we insist on mining on here, is, "it's normal for people who are experts in their fields to be middle-aged, actually"
