I don't think you get what the problem is. Yes, these people are wizards who learned magic. This doesn't tell us anything about how common people who can learn magic like this are. Average age of an astronaut is 34. This doesn't really tell us anything about how hard it is to become an astronaut, only about how fast the people who have an aptitude to begin with can do it.So, the fact that I could find artwork of a 30 something professor of magic, who was hired by a magical academy, doesn't tell us how quickly a magical education system could train people to high levels of magic?
But alright, fine, can't use the Strixhaven artwork. How about the Archmage from the MM, am I allowed to use that? Guy looks like he is in his thirties, human, and he has access to the "highest levels" of magic in 9th level spells. Is he also a specialized outlier who we can't use to determine how long it might take someone to learn magic?
What about Rath Modar and Azbara Jos, found them by searching DnD beyond. They are Thayan wizards, high level casters, and they also look middle-aged, not old. And they are still human.
How many "outliers" would I need to find before it becomes obvious that they aren't actually outliers?