I'm at a loss as to why you think the structure was a 'mess' or what you mean by 'badly put togeather'.
I mean it was flabby, lazy, and not well written.
Compare it with the data loss episode, which was much better, structurally. It had flow, more concision, and, structurally, more purpose.
As for the "narrative arc", in what sense are you able to assess it given that, by your own admission, you've only watched two episodes out of three seasons?
I'm talking about that episode. Narrative arc is a more detailed way of seeing the "beginning, middle and end". All stories, no matter what the style or subject, need to build a story, using various devices (such as tension, suspense) through a narrative arc. This arc is usually described as having seven points, but that isn't important here. What is important is that in this episode, Iannucci seemed to rely on the actors, and especially on the character of Malcolm, in lieu of any clearly defined narrative.
If you'd just said "it's not my cup of tea" then I'd have thought fair enough, but I don't see any validity in your more substantive criticisms which seem to me to be either to so vague as to be meaningless or criticising the show for what it's not supposed to be.
Well, it's just that it
ought to be my cup of tea, and I like (some of) the writer's previous work.
I don't think my criticisms are vague. But I do concede that they are of only two episodes. (And the film, which I thought was OK, but promising. Which is why I thought I'd check out the show, to see if the problem was that 90 mins was too long for the concept. I suspect it's just that the idea has run out of steam somewhat, and that if I watched series one I'd see more life and purpose).