The fetish content feels more or less like a play on the creator's part of trying to be provocative, to make an ironic statement, which is a shared concept about would-be-auteurs and while that's all well and good; I can't say it succeeded. It felt more or less like a Suda51 game, post-Killer7, it badly atttempts to conform some sort of message through bloated dialogue, with a whacky setting. From my perspective, it's story full of lies. It pretends to be something that it’s not. Oh yes, that’s the point of fiction, but for a show that’s carried by dialogue, the characters talk a whole load of nothing. It’s self-aware, but a story that builds itself entirely around being self-referential lacks its own soul. I find this all difficult to reconcile with in my head. It’s hollow, bullshit art – lies feigning at truth.
It felt like a collective series of brainstorming ideas in the author's mind, sloppily converted to paper; There's a little bit of wit there, it seems somewhat personalised, the conflicts too unrelatable, despite the characters having understandable problems.
I can see your point of view, though I I disagree a bit with it.
To me, the factors revolving around the fanservice aspects are just that; fanservice. Plain and simple. If there exists some underlying element within them, I'm not seeing it (except when they establish another dimension on a character's personality, but those are few in between). While I can agree on it being aimless and pretentious from time to time and more often than not likes to portray simple concepts in the most round about, overcomplicated manner (which it actually makes fun of)--I wouldn't conclude the entirety of the show as hollow or "bullshit art".
The Monogatari series are a lot of things, and quite "unbalanced" in their delivery which each consecutive season. While the general approach is generally similar, the show does thread between a line of portraying the narrative as a means to facilitate the fanservice, the various “offbeat” conversations that occur and artistic imagery, with where the dialogue, characters and art is always pointed and actually serves a purpose to complete the narrative. But what lies in the heart of the series (and the main reason why I love it) is its play on "authenticity vs. inauthenticity", which is something what you actually said yourself--it is a story about lies. Or more correctly, about liars.
The series is about people who lie to themselves and in turn distance themselves from parts of their own personality, or replace their exterior reality with a more joyous and less judgmental internal one. This makes it a fabrication, a false self and a false reality, which in turn spawns aberrations for each respective character in various forms. E.g. Nadeko has a snake, which symbolizes transformation and is something that she is desperately struggling for but feels unable to do so due to the restrains that have been brought upon her. It certainly is a very extravagant portrayal to create a certain relation to the viewer, but I found that it manages quite well in its delivery for most cases. For a lot of characters, it depicts the notion of how incredibly comforting it is to hide in personal realities, in where you make the world where the rules make sense and your failure can be comfortably quarantined as not your fault, which is a state I find a lot of people confine themselves into.
While certain characters are rather lifeless in their initial appearance and are more a pile of constructs and contrivances, rather than being a character on their own I can't help but appreciate how well it is done in the framework of the story. This goes especially to Mayoi, whose character is put together because she contributes into an entertaining whole (in which her arc has Araragi forcing Mayoi to accept his help, but ends with the reveal that he is actually the ones who needs help because of his own actions), despite the taunting of perversions. Eventually she is given evident characteristics to stand on her own, but happens much later and most of her appearances are thrown into a state of serving the fans.
In terms of artistic imagery--the show's primary strength revolves around the concept of experiencing each characters view through a "character lens"; in which you as the viewer see through their imagines and not what actually exists. You can notice this by there not appearing any people in public places, since they aren't relevant to the protagonist and doesn't simply matter in his life. The combat and gore are exaggerated and overplayed due to Araragi actually feeling the pain and making it "bigger" than it actually is, and the landscape usually changes dramatically in an instant when his mood changes (e.g. being hurt and having Senjou appearing, shifting his complete focus on her and not anything else). The objects are similar, since it is the way he sees the world. This changes from time to time within the series, wherein it starts showing allegories in visual representation.
The Monogatari series has its flaws, and there are plenty of them, but by the end of the day I think it is a pretty extraordinary show on its own right, albeit unbalanced in its representation from time to time.