It goes downhill from Season 4, and even Season 3 was meh. When you see the top comments complaining about the storyline and pace, then it's pretty bad.
I agree with everything the comments before me say. Lemme try to come up with new points...
The art isn't something that I'm a huge fan of. It's nice, yes -- in fact, it's VERY nice -- just look at the background and how much work that takes! But it's this type of 3D digital kind of art (similar to Orange Marmalade, another series I disliked...) that is unreal that makes it off-putting. And towards the end, because of how draggy the story was getting, I was just skimming over the story and not appreciating the art. :/ Sorry to the author and assistants.
The character development is also there, but it becomes tiresome to keep track of as they all go back-and-forth and change their minds constantly. At that point, it's character inconsistency and you get whiplash trying to keep up with their incessant monologues and dialogues. In the end, I liked none of the characters.
One thing I had a problem with, which is probably an unpopular opinion.
I really didn't like how Dongtae and Mio were "explicitly implied" to have had sex. Considering that romance isn't the main point and "doing it" wasn't quite a significant plot point (and if it was, then it wasn't emphasized enough), it was just unnecessary and that left a bad taste.
The ending... is a disappointment.
That crazy pink-haired girl kills people, yet she gets a happy ending. What's up with that?
And the invincible Muyoung who is so full of hate just ... gets put to sleep? The accumulation of hatred was so easily pacified? Why did his backstory even matter...?
Same with X, who got taken care of just like that. His ending was ambiguous and I can't tell what really happened to him, which is a disappointment.
And weirdly, he was born within the 20th century (the bulldozer was invented in 1904, and it was pictured in his birth village), yet he and Muyoung kept going on about how "old" they were. In reality, they probably can't even match up to the oldest person alive LOL. I honestly felt like this was a letdown and even a plot hole.
Hyun Choi was such an interesting character, yet he ended up spineless and useless in the end. What a shame, because he had so much potential.
The backstory for Eunjoo came WAY too late, that it wasn't even important by the time it was revealed.
That swimmer guy isn't even important, but he gets an "ending" too. Why?!
Would've rather we see the levitation girl come back, but no, she just disappeared after the hospital fight scene.
Dongtae wants to fulfill everybody's wish, but he only fulfills the wishes of the people in his immediate circle. LOL...
Also, he became ridiculously whiney when he went back to having 0 dice in Season 3. That arc started off fine, but it dragged on too long and his annoying personality became increasingly unbearable.
I have complaints, but I DID enjoy the series. It's a pity it ended the way it did, but it's a series that the author put hard work and effort into.
I seriously loved episode 380 -- love how real it is. It was a really nice touch to the webtoon.