Many young professionals do not want to live in ethnic enclaves.
What makes things attractive for ethnic groups is not that same as what makes a neighborhood attractive to young professionals. Ethnic groups like Hamtramck because its a bargain. Young professionals equate affordability to unstable places. Young professionals care less about dollar stores and ethnic groceries than they care about starbucks or whole foods. In short, while Hamtramck is very cool to a large population of city dwellers, young professionals would rather not live there. Heck they might have to share a flat with someone with ESL!