Is to Christopher Guest as The Departed is to Martin Scorsese: nothing but an amalgamation of all past motifs and hallmarks thematic and stylistic; wildly disappointing for its lack of progression and utter inability to add anything new to the de rigeur mix; still, being as it is who it is, doing what it is they're doing, ceaselessly entertaining and, more than once, sit-up-and-take-notice good.
Many things oughtn't to work but do: the tired "what is this Interweb thing?" bits, the Useless Agent (really, Eugene Levy and Stephen Merchant's Extras character are basically the same person), Catherine O'Hara doing pretty much the same thing she always does, albiet incrementally more icky and disturbing than usual when she puts her mind to it. Hell, even the mere presence of Ricky Gervais really should just feel extraneous and gimmicky. ("So...") And maybe it's just because you so want it all to work - it's Guffman with movies! - but it kinda does.
Probably the only actual innovation is the film's approach to the question of, "who's filming this?" Guest, having declared the "mock-u-mentary" genre to be silly and something he wanted to move on from, here gets his usual gang to do their usual schtick in a curious blend of staged drama and the standard verite hijinks.
This is a deadly brew: it would be all too easy to see the mix of doco and cinema as an excuse to not tell fictional stories very well. Where dramatic filmmaking is a process of adding layers and elements until the story is completed (or abandoned, or shruggingly released into the ether), documentary is about stripping extraneous elements - dodgy sound, unwanted camera moves, the myriad ums and ahs that make up most peoples' unrehearsed parlance - until the story reveals itself. Go too far and the process removes honesty; not far enough and we might as well just pay to watch the rushes.
But when you're telling fictional stories in a quasi-factual style, the temptation - succumbed to by legions of amateurs - is to use the "mockumentary" label as an excuse for Not Getting It Right. The resentment toward these types potentially ascertained by the more astute reader is borne out of the laziness on show: yes, there is an awful lot to get right in a film, but if you think that a couple of to-camera addresses from your protagonists gives you carte blanche to not even try, you must think your audience pretty dumb.
So For Your Consideration's decision to abandon the baldly documentarian style of Guest's previous work - there are no addresses to camera, and many scenes play out in the dramatic convention of shot-reverse-shot - might seem at first like Guest embracing irrelevance by giving himself even less work to do. Which is not the case: everything in Consideration feels well-put-together, layered over itself to feel lived-in without appearing sloppy.
It's just a shame the same attention wasn't paid to taking the characters and story to a few more interesting places. If you pool your knowledge of the Hollywood-backstab pic and your experience of Christopher Guest movies, you'll probably be able to name most of the plot developments without even seeing the movie.
Unless you weren't familiar with either genre. In which case this could be one of the best movies of the year. So...
 He's right: of all the fake-documentaries made in the world, 95% are amateurish crap made by mouth-breathers who can't be bothered with finickitty cinematic concerns such as story, cinematic grammar, competent camerawork, &c, &c.