American comics have literally never been more diverse than they currently are. Your argument honestly has about as much validity as if I were to come in and ask "Where is the variety of genres in Manga?!" and used the dominance of the mainstream Manga market by adventure stories.
Superheroes are the most popular but if you want comics about this...
> Where's the comics about cooking? Soccer? Basketball? Being an office worker? Farming? Running a restaurant? Etc?
All you have to do is look.
Incomplete Works by Dylan Horrocks (various slice-of-life short stories)
Dragon Hoops by Gene Luen Yang (Basketball)
Spinning by Tillie Walden (a memoir by the author about being brought up as a competitive figure skater)
That Can Be Arranged by Huda Fahmy (Story about trying to find romance as a Muslim woman)
The Nao of Brown (A woman struggling with OCD tries to get her graphic design career off the ground)
Local by Bryan Wood and Ryan Kelly (short stories about a young woman backpacking across the USA)
That's just a handful I named off the top of my head.