That's not really true. Generally in every sport athletes make many mistakes when they are very young. It would be shocking if not considering their experience. It's their peak (somewhere between mid/late 20s to mid 30s) where
I don't understand why we talk about the sportsmen in F1 in total isolation to athletes in many other disclipines.
Top athletes in other disclipines decline and make more mistakes as they age ( *cough Roger Federer cough*). It's human nature to an extent. Yes, mistakes suck, but we shouldn't be thinking that athletes become more and more perfect as they age...and therefore Vettel is the anomaly. Because that's not the case in any other sport. Actually Lewis is the anomaly because he's getting older, but not making mistakes.
20-30 seems to be where the peak is physically. Beyond 30's men should be declining physically due to lower testosterone levels. Every person is unique, but generally decline starts in 30's.
they should hit the optimum balance between experience/consistency/performance.
30-32 is still prime for most, in most disciplines in fact.
The Roger Federer example is valid, but he is 38. There are old athletes who continue to stay relatively solid but are lacking performance (e.g. Kimi), but also older athletes that get more and more error prone, that's indeed depending on the person. But Vettel isnt this old yet.
So yes, Leclerc doing so many mistakes is naturally expected, while Vettel not so much. Of course reality then always looks different from person to person (and Vettel is maybe a extreme example of that) but considering the athletes experience and age is important in context if you try to compare driver and their tendency to screw ups. A 22-24 year old who is a couple of years in F1 is much more likely to screw up than a driver in his early 30s and more than a decade under his belt, hence why I disagree with his verdict on how Vettel's Ferrari time compares to Hamilton's McLaren time.