You seem to be reading too much into this expression. This has nothing to do with swallowing anything, and 'gutter' does not mean 'throat'. Literally, the gutter referred to here is the channel running along the edge of the road. Figuratively, it means the lowest point, especially in financial and social terms. If someone is 'in the gutter', it means it is as low as they can get. Edit: Now you've given the context, the meaning is clear. You're also right in your second assumption: he's insulting the driver with a colourful expression meaning that the other person is totally useless at his job: he has no skills whatsover. The implication is that even if you asked him to do the simplest job in the world, he wouldn't be able to do it. 'Kicking sh*** along the gutter' is, needless to say, a fairly easy task, but this person is supposedly so incompetent that he couldn't even do that. Note that this is not an accepted idiom: it's only the context which tells us what the speaker means. The standard and equally vulgar British English expression which is usually used to describe someone incompetent at their job is "He couldn't organise a p***-up (vulgar term for a drunken party) in a brewery". This is universally known and understood by BrE speakers, and the audience would recognise the expression you've quoted as a variation on the same theme. It would be interesting to see how people would express this idea in other languages, not to mention other varieties of English. I hope that helps.

Thank you Lin, so sorry, you were right, I didn't provide the context the expression refers to, thank you for pointing it out. I added a comment with details about the film scene. Probably you are right, as La Liseuse suggested. Hopefully the details can help you to get deeper into that.

As correctly asked by some of you, here's the film scene where the expression came out, just to give you some hints to help me. There are two lads in the parcel delivery centre, early in the morning, loading their vans. They're "self-employed" franchisee drivers, working for a delivery firm (that's a movie about gig economy), one of the guy at his first day at that, the other providing guidance and tips. The seasoned asks his pal whether he has any more questions but suddendly another driver next to them comes in saying ironically "I've got a question: when are you gonna get these f****g parcels out?" pointing to the newbie's boxes. The experienced replies "Less your cheek,right. You were a donkey for the first month" and then to the newbie "Ignore him, he couldn't kick shite along a gutter. He's a sub-contractor driver, he gets 70 pounds per day". 70 pounds is a way lower wage compared to the average provided to non sub-contractor drivers. To me the ironic question of the disturber was actually revealing frustration, hence that's why I thought "he couldn't kick shite along a gutter" was a way to express that the disturber is fed up with his situation despite he can't do anything but carry on. But yeah, maybe the real meaning could be that the disturber is a sort of an idiot, not very good and quick at his own job, so he has to settle for worse work conditions and a lower wage.

Hi Diego! Personally, this would make more sense to me if I could know what was said (or what happened) before and after this expression, to get a better understanding of the gist of what is being said. But you are correct in assuming that "gutter" always has a negative connotation and this expression could just mean that the person has stooped so low or reached such a "bad" place that they are permanently "in the gutter", and being in the gutter means that that person might come into contact with the bad stuff "shite" or (poop) which might ordinarily be found in a drain. So it means that the person is going to be in a bad place or situation.