Minor spoiler warning! Although I only talk about indirect things, at least one, regarding MC's personality and some of the beginning set up.
Either way, I tend to have a problem with stories that invoke a long period of time, like thousands of years, for MC to train and supposedly grow, but never change MC's personality. This story suffers from that. MC spends 1,000 years training, living, and most importantly reading ALL OF THE BOOKS IN THE WORLD, to include philosophy, religious, critical thinking, etc. books that would change his thinking significantly from an edgy teenage-like mindset to something with a lot more wisdom and thought at approaching subjects and issues. Not to mention he'd have read all of the self-help guru books, many of which deal with introversion versus extroversion.
Yet, MC spends a lot of time upset that he has a maxxed out stealth attribute that makes him invisible other than when people directly focus on him or something within his immediate vicinity and then they interact with him or if MC interacts with them. He wants people to notice him so badly, yet when they do, MC acts like a jerk, spouting Mcedgelordy things that peeps online only spout about heroic characters, for example, when one guy tried to make friends with MC in his own way by creating a rivalry between them. MC proceeds to call the guy gutless and pointless for wanting to do that in his mind, doesn't even offer a response to the guy, right after being jealous of the guy for being able to talk to people properly instead of MC being unable to talk to people properly. Came off as really jealous and insecure the way he responded to the guy in his thoughts, but MC did this every time someone would talk to him RIGHT AFTER HE COMPLAINED THAT THEY COULDN'T SEE HIM. He'd get annoyed they were trying to make friends with him for whatever reason, respond awkwardly or arrogantly, or not even respond at all.
Everything is your typical system apocalypse manwha flavor. OPMC who wants to be a loner (but he really doesn't, yet all of his actions forces him to remain a loner with the exception of those characters the author forces in MC's orbit), dungeons, mana, monsters, game stats, game skills, etc. appear in the modern world. MC spends a lot of time doing quests, declares he wants to protect his family but never takes the reasonable, strategic option that does like forming alliances with organizations that MC could utilize to send agents to watch over his family while he does stuff. Even when these MC's have all the leverage to negotiate their relationship with said organization. Nope, they choose loner mentality because that's what edgy readers think would be the best strategic option in those situations. Even in this story where author has MC complain that the tasks given to him by "heaven" to hunt all of the abnormal monsters is too much for one person, MC only thinks about finding one character because he wants to use them. Not form an adequate relationship with them after 1,000 years of being alone save one person😕??
As I said, I tend to have problems with stories like this that front load 1,000 - hundreds of thousands of years on a MC and then don't change them. They always remain socially awkward teenagers in personality, character development, etc. In this one, MC spent 1,000 years alone minus one angel who he said only visited him once a week, yet when people appear, MC starts acting like an ultra introvert who doesn't want anyone to bother him, doesn't want to do anything that puts him on the radar (while complaining that he's auto-invisible based on his stealth) and doesn't want to engage in any kind of adequate teamwork that could network build, etc.
it also didn't help that the whole mask + uber stealth + auto invisibility stuff reminded me a bit too much of "Be an Adventurer! - Defeat Dungeons with a Skillboard" MC set up who has the same three qualities, the only difference is that MC is actually happy when people talk to him and want to form teams with him and network him and that's the running joke with him, that he gets entirely too excited when someone sees him and acknowledges him and talks to him because he spends most of his time invisible to others. At least that makes sense for a character who can't control his stealth skill and seeks companionship. This character in this story claims to seek companionship (to be seen) and then pushes it away when someone approaches him. Which was annoying.
Along with that the world in some places is inconsistent. As usual for these system apocalypse stories, the author invokes that conventional weapons (guns, nukes, etc.) don't work, yet in one chapter says the army shot up some monsters and thus when they process the bodies they're all messed up, then in the very next chapter say the guns don't work again. Yeah, you get stuff like that along with the aforementioned MC inconsistency.