I think what it is is that the people who are so burned by their own expectations not being met, you aren't wrong to feel that way... but I think a lot of how it's put is evoking a response of "Oh. You are mismanaging your expectations."
Like when you see a character's third appearance reveal more about the character that changes how you look at the character, and think "Wow this is a complete reversal" and not "Oh, here's more depth to this character", you aren't wrong to feel slighted but people will try to push back that you should think it's the second thing, not the first. It's... I feel like some people have been going into this, at chapter three and since, actively hostile? That's not everyone who is critical, there's plenty of criticism that's fair or that I think hinges on a disagreeable interpretation—but "I read it differently" is not "They read it wrong", that doesn't mean it's unreasonable. Ultimately, if the story came off to you as bad, that's a failing of the story to reach you properly, and you're welcome to complain about it.
But I think in trying to say factually there are problems and you need to acknowledge that they are problems even if you don't care about them, people keep showing that they've gone in looking to find more evidence for the fact it is bad, after one thing they didn't like happened. I don't imagine that's on purpose, generally, more of a heightened alertness after one problem... But I think that way of reading something will actively make the experience worse in kind of a self-fulfilling problem type way? (Unless you enjoy hating on the work, in which case it's a most fun way to read it, but that doesn't seem to be the people commenting negatively here.)
(And there is absolutely the counterpart where you go into something and contort everything and anything that happens into evidence that this is the greatest story ever... But that seems a fairly pleasant way to be systematically wrong about a work. At least if you stick with enjoying it and not delve into arguing about it forever, but alas seeing people doing the latter is how I know such readings of fiction are possible...)
Ultimately there's not really anything to do but argue over particulars if one is interested in doing that. I think the instinct, on either 'side', to respond to a vague or general sentiment with "You're wrong because you're ignoring/misunderstanding X, Y, and Z" is, while understandably human, pretty fundamentally misguided.
I like silly pointless arguments with zero stakes and long drawn-out discussions of particular points because I am That Kind Of Nerd, but I do worry a bit that this will be arguments forever instead of appreciating the manga or having discussions about how it raises and handles ideas. And that'd be a shame.
