You have Liera who, at first was a higher existence that was slightly moved by Yu Ilhan's effort. Later on, all of a sudden, Liera comes back and is head over heels for him and would literally do anything for him. A very huge personality shift with no consistency. Not to mention that Ilhan is dense? Didn't he say that he "likes" Liera way back after the 1st great cataclysm had occurred? Isn't that why he never looked towards Kang Mirae or Na Yuna as potential lovers, as his standards were very high? And then, he becomes dense towards love all of a sudden and doesn't know that Liera is infatuated with him. I'd assume that, after 1000 years spent on Earth and reading every book in the world, wouldn't he have read tons of Psychology books, self-help books, and love stories? He shouldn't be that stupid.

I, personally, never enjoyed the idea of an overpowered protagonist that then, later on, has characters that piggyback off of him. Mir is one such character. You're telling me that the amount of effort Yu Ilhan did was somewhat easily caught up with just because Mir is his "son"? Sure he had his little moments of effort which the author just threw in, but 90% of his strength was just passed down from his parents and it hardly seemed like he struggled at all, unlike Ilhan who struggled in the first 1000 years. And then you have his parents who had little to no presence in the novel and it already seems like Ilhan's 1000 year effort was, in fact, a "talent" inherited from his parents? It's like the author enjoys writing about the overpowered MC with the huge gap in levels compared to other characters yet is also desperate to play catch up with all his other characters.

Do you really think he became a dropout due to that? REVEALED PLOT ISN'T ALWAYS THE TRUTH.

Supposedly the 'monsters' are immune to the original rules of the world (physics) in that they are supposed to be immune to human innovation and science, being the fantasy creatures that they are. They even explicitly state that not even nuclear weapons would be good enough to stop them. However, the MC builds a pile-bunker (well within the reaches of human understanding/knowledge/physics might I add, nothing magical about a damn pile bunker) and uses it to easily squash and one-shot high-leveled mobs

MC spends only 250 years to read every single book in the world. On top of this he traveled to every country in the world and just about learned every single language. You have to consider that, even if this was possible, you'd have to be some kind of freakishly fast speed runner with a perfect memory and a incredibly powerful comprehension (i.e. You basically have to be a genius). Despite this though, the MC still acts somewhat braindead at times and you often question how smart he really is.

What's also hilarious is that he spends an additional 50-100 years learning how to be a blacksmith, because apparently forging swords trumps nukes. And apparently, learning how to become a master blacksmith takes a quarter of the time it would take to learn all the languages, read the books of, and visit the countries of the world.

There is no explanation, or hints about why the MC was left behind and thus unable to learn how to control mana. There is no explanation why the angel that visited him could not teach him mana control in his own world, or why building up his body when even nuclear weapons supposedly won't work against these mobs, what is a karate chop or a round house going to help? Basically the MC memed his way into becoming a proverbial Chuck Norris and now somehow he can compete with people that have powers that allow them to surpass nuclear weapons (checkmate, Gandhi).