With time you learn that really paying attention is not that important as truly great films will amaze you even if you haven't slept for 20 hours and want to die.
There are a few films I kind of want to see just to "keep up" with this or that aspect of the culture, or to find out something firsthand, but otherwise am not that interested in. Those I can sort of half-watch. But I hate doing that and it's rare.
Of course, ideally, you should be in the right frame of mind 100% of the time, but this is impossible unless you only want to watch 100 movies a year.
That "right frame of mind" you're talking about, whatever that is, can be trained, too. You can practice endurance, etc.
Regardless, I have learned about myself, over the years, that when I can really focus on something I can notice a lot of stuff about it. A lot of themes, connections to other things (intentional or not), nooks and crannies and implications. But it takes a lot out of me. It is difficult to know this about myself and then dial it down and be content with some half-measure. It ends up feeling pretty all-or-nothing.
My philosophy here is that there's no free lunch. You can maybe improve things around the margin, but I don't think there's a way to deeply focus for much longer periods of time. It's like sprinting: by definition, it's you running as fast as you can. You can get a little better at it but if you think you're sprinting MUCH longer, it inevitably means you're not running as fast, trading intensity for endurance.
Incidentally, I believe that we should rate films right after watching them and then stick to our initial feelings. I think that's the most sincere approach, too, since you cannot be swayed by your post-watching thoughts (which isn't that bad - happened to me a few times) or other people's opinions/hype (which is pretty bad).
All that said, immediate impact matters, because it's not fair to say "oh, you can't appreciate this until you've seen it a few times." It's a balance. The same way an episode of TV has to be a self-contained unit and service a larger world or story.
All this really nets out to, then, is that the idea of a "rating" is fundamentally flawed to begin with, because it can't account for all this, especially if it's unalterable.
Like which ones?
They largely waste a lot more time with needless subplots and distractions that do not strengthen the main message.
It's just a different art form, what would be a waste in a film isn't a waste in a series. The whole point of a series is to be able to spend more time on things that aren't just constantly driving towards a single resolution. More character-based, more fleshed-out worlds. And of course the concentric narrative challenge I mentioned earlier.
The older I get, the more I appreciate simplicity and sincerity in films. A single camera pan from a Shimizu is more impressive and says more than a whole season of a TV series. I think most TV series are too focused on telling the story (like novels). Kinda explains why when an auteur goes in a different direction with their TV series, they're accused of 'style over substance' and whatnot.
I agree with the comparisons to novels. In fact, a lot of classic novels were released a chapter at a time.