I think the problem is really more basic. People like to identify with the protagonist/POV character, and very few of us like to think we're dumb. Most of us prefer to think we're equipped with at least average smarts, or at least have above-average skill in something that makes up for conventional paper-pushing braininess**. Most of us even enjoy stories about heroes or heroines who are smarter, tougher, and/or better looking than ourselves. But put somebody in the protagonist slot who is demonstrably stupid, and people will tune out. Even in "Flowers For Algernon", the main character moves along the arc from slow and dull to supergenius and then back to slow again, and therein lies the tragedy that makes the story work. If Charlie stays dumb all the way through, where's your story? Even in an ensemble cast, the dumb guy (or gal) isn't going to be the lead; they're going to be a glorified spear carrier or the Boy Blunder whose screwups require the rest to bail him out of trouble.
So, no. You're not going to see stupid people carrying the story, or of you do, nobody's going to like it unless it's an obvious parody.
* I might go so far as to argue that Bertie's not really dumb, he's just plagued with the kind of relations who pose the kind of problem that only a genius can solve. Otherwise, he's a solid English stereotype gentleman who might be a distant cousin of Ron Weasley.
** We tend to overrate the bookish, intellectual skills in this culture, often to our detriment.