I have met people with 5 years experience who are significantly more capable than others with 15 so I don't think time is a good metric. A lot of it is about attitude, some of which comes with age, but some is more intrinsic to the person.
Take one of these "people with 5 years of experience" that are great and wait until they have 10 or 15 years of experience. Would you expect them to be a better or a worse engineer then? You need to compare apples to apples, i.e., talented engineers to talented engineers - and in this case, experience often makes a big difference.
I understand that, in our field, there is the impression that older engineers don't "keep up with progress", but this stereotype is just a form of ageism. That might be the case of bad engineers, those who were never great to begin with, but a talented engineer with a lot of experience is really hard to beat. These people can make design and architectural decision for million/billion dollar projects that an engineer with 5 years of experience would never be able to make confidently.
In a nutshell, you can't take experience alone as a predictor of performance, but there is a strong correlation between experience and proficiency.