Out on his own for the first time with no family or support, a mentally-challenged man with impulse control problems must overcome his limitations and face a series of cruel and indifferent characters as he chases his dream of a “normal” life.

I kind of remember this logline, and it still makes me think of Bad Boy Bubby (http://www.imdb.com/title/tt0106341/). I join the previous comments when they said that it's too vague, it lacks specificity. Your logline could apply to Bad Boy Bubby and Beign There (where a simple minded gardener who spent all the life in a garden explores the outside world after his master's death).
I think this archetype of the fool can still generate excellent movies, including your movie: you "just" have to make some creative decisions and nail the main elements in a coherent and original structure.

Agreed with the above comments.

Also what does "...impulse control problems..." mean?

The logline lacks detail, uses generic descriptions and doesn't describe a clear goal, as such the plot is vague.

It's very hard to imagine the type of action and genre of the film.

I agree with DPG, stating a specific disease can cut out a few words, and the fact that it lacks an inciting incident. Also, what is his motivation? Why is he not happy with his life the way it is? What drives him to seek what he thinks of as a 'normal' life? Perhaps using " an impulsive man' rather than "a man with impulse control problems" is more precise and also cuts out extra words. One last thing, maybe try to narrow down to a specific antagonist, rather than "a series of cruel and indifferent characters" you could try focusing on one (wo)man or just try to describe how society is cruel and indifferent to people who are mentally challenged.