It depends who you ask.
If you asked the average 11 year old on quora they will tell you “well I can run 10.3 and all I do is play video games all day so I think the average adult should be around 7 seconds.”
However if you ask me, a person who is in touch with reality and doesn’t feel the need to lie on the internet I think most people should feel bloody good about themselves if they are hitting a time anywhere between 13 and 15 seconds, this would probably be faster than a good 90% of the population.
Sub 11 is out of reach for all but a few.
Sub 13 requires a bit of physical gift for men and exceptional gift for women. This would take a lot of training and not everyone could do this.
Sub 15 is attainable for most men and maybe about half of women with training. This time is typical for fit people who have played a fair amount of sports in their life and have been competitive in some way at some thing for at least a couple of years.
Sub 17 is attainable for most women with training and expected of most men without training. This time is typical for people who have never had a weight problem.
Anywhere between 18-30 seconds would be average - considering overweight is average.