I'm not claiming it's perfect but some of the actors do get the basics down. I grew up and lived in Baltimore City for 23 years, have friends from school who are still living there in middle age, and when the show came out we all thought it was a decent representation of a set of fairly difficult accents and dialects.

I think what makes it hard to see for some is that Baltimore has so many neighborhood based dialects (some of which are further broken down by ethnicity), and if you only grew up around one of them you won't notice the others. I went to magnet schools so I was exposed to so many of them. The Dundalk version is different than the Essex version, which are both very different from the Lauraville version or the Parkville or Owings Mills versions for white people. Then you get into the Black variants which again differ based on neighborhood, as well as the Korean and Vietnamese community variants (though I found those tended to be pretty influenced by the Black folks in the neighborhoods they often shared).

So, for one show to kinda hit on a bit of that variety, often based on where the characters lived or worked, is a pretty big feat.