I never got around to watching it when it came out, and I think I'd completely missed the critical reception and box-office failure it received. Which saddened me to read after the watch, I have to say, as I was really happy to have watched it.
For those who don't know the film, I personally liked Roger Ebert's review (with whom I generally vibed). It was polarising, and genuinely confusing if you want to "understand" a film, while also potentially being vacuous and overwrought. I'm not going to say it was a good film or recommend it to people. If it's for you, you'll know. All I'll say is that it was, for me, a very good kind of film and generally well executed. Some ambitious film ideas and high level or broad concepts put to screen pretty full-throttle.
I haven't seen a film in this general category of viewing experience for a while (probably entirely on me). Last probably would have been 3000 Years of Longing and maybe Twin Peaks S3 (I count that as an 18 hr film), and then Aronofsky's The Fountain (to which Cloud Atlas is probably the closest sibling I can think of).
Without getting nostalgic about films or critical of the current era (I'm not on top of film enough to do that) ... I was certainly reminded that I need to revise my film/TV diet. It re-affirmed for me a sense that films are more powerful than TV and that this era of TV has been productionised in a way that seems to suck the art of it.
As for what the film was actually about, I think it's much like 2001 A Space Odyssey, it's both obvious and confused/inexplicable. I'm sure there's a whole technical breakdown one could read or endeavour to create oneself, but I'm happy to have watched it once and perhaps revisit it again later to try to pick up on all of the connections I'm guessing they wove through the film, in large part because I think that's in line with the spirit of the film which I'm happy to embrace.
Beyond all of that, but kinda connected I think, was to reminisce about the Wachowskis' career, where whatever their flaws, I think I prefer them making things to not ... there's a certain essence of good-hearted and ambitious geek-dom to their stuff that I'm just happy to watch (including Jupiter Ascending and Matrix 4).
My feeling was that you need to pay a minimum amount of attention to get a feel for the film, probably more than most films. But that's pretty easy to recognise early on and the film kinda weans you into realising this.
But beyond that minimum amount, it's up to you how much attention you want to pay, where you can opt more for the vibe of the interconnected stories, or try to be super detailed. Unfortunately, I think there's a genuinely toxic reaction from some viewers that hates a film that demands some amount of "work" from the viewer, as though the film has done something wrong. Which is toxic for a few reasons, but one sad one I think is that it destroys the idea of watching a film more than once in order to understand it better and just going along for the ride the first time.
I think you are giving yourself too much credit. It's not that the film "requires work", lots of films do. The problem is, there's no payoff for the work involved.
The Lord of the Rings films are 12 hours long with a ton of characters. You can easily miss the fact that Aragorn is some ancient foretold king, so the ghost army doesn't make any sense. Also, it wouldn't make sense why Denethor is angry at Gandalf coming to help him.
The films are enjoyable if you don't pay much attention, because they have a lot of action and cool lines. But they also have an intricate story that improves when you pay attention and watch again.
Cloud Atlas tries to be intricate but the story is just not good. "We are being reincarnated" isn't an original idea. And the execution is tedious.
Honestly not sure what you mean by that ... what credit am I giving myself?
Well, I think that depends on what you want. I for one was very happy to watch an attempt at putting reincarnation to film. The core idea of reincarnation doesn't need to be original, and I don't think the film itself has any sense of that, in the same way that LotR (books or films) doesn't try to claim that geography and history are its own original "ideas".
As for whether the story is "good" ... well, the core of the story is kindness, self-discovery and finding a way to live with or "fight" the evils of the world, along with some meditation on "what is the significance of one's life". Like I said, I'm not keen on describing this as either "good" or "bad", but I'm certainly happy to watch it and I'm sure plenty of other people are too.
Otherwise, comparing LotR to Cloud Atlas seems strange to me. The former is essentially lore based while Cloud Atlas is intended to be self contained. There are things in the LotR book/movie that just do not make as much sense without then reading the Silmarillion and/or the appendices, and all of the internet dissemination of this lore for those who haven't read more deeply is quite extensive ... it's basically top-tier fantasy world building gone mainstream ... having details discoverable beyond the film, and which have been "discovered" by many, including it seems yourself, is by design, before the films.
But you don't have to watch Cloud Atlas more than once, it works just fine on a single viewing IMO, and is clearly not intended to be a world-building exercise, in large part IMO because it is very much about our world, here and now.
But if you don't like it or find it tedious ... that's all good, I get it. I just think there's something misplaced in trying to approach a critique from a relatively objective standpoint of "done well" or not. It's a film that's very much about a vibe or feeling IMO (which Ebert was always pretty good at picking up on I think, thus my link to his review), and either you're receptive to that vibe or you're not.
Subjective art ... is good ... wonderful ... vital even.
And that's part of what I appreciated about the film, it seemed from the outset to have a relatively personal essence that you either connected with or didn't ... which is what my comparison to some of the modern stuff, especially TV, that I've consumed lately. There's nothing quite like a "personal" work.