Solo Leveling was a massive disappointment from the hype that has been risen from this anime adaptation. It definitely panders towards a certain demographic, and that demographic being power fantasy enjoyers and bland story enjoyers. This was incredibly uninteresting, basic, and downright confusing. I scratched my head at not only the main character's actions but also the continuity. For example, during a fight the main character uses heavy acrobatics, despite having a base stat for his agility, or the fact he says nothing is on the level of his opponents when he fought S-rank monsters before. These are nitpicks however, and nothing substantial I would really care about.
What I do care about when I'm watching something is, is it engaging. Are the characters well designed, have good stories, and have fun personalities. Is the world interesting. Is the story being told powerful and executed well. Was the music a highlight. And (on occasions) does the art style improve the experience. Solo Leveling had great music thanks to Hiroyuki Sawano, but everything else I mentioned is basically non-existent. There were only 2 characters total that I had any actual connection to and they were both side characters. (Jinho and Mr. Song.) But they themselves are really nothing special at all. The world feels bland not in the fact that its the real world but the fact that the premise of gates feels underutilized. We're told they have effected the economy, politics, and all sorts of factors yet we don't see any of that really. It feels fabricated and not immersive or important. I actually enjoyed the first four episodes the most, pre sigma male cool sexy awesome morally-right Sung Jinwoo. The most bland protagonist that is both unlikeable but also turns dense for some reason, and just suddenly stops seemingly caring for people. He gives little in the way of sympathy, barely ever even smiling at his only companion for the majority of the show, Jinho. The girl he promised to go with when he survived and had PTSD from their dungeon is completely ignored and seemingly forgotten about. He literally sees her fighting after clearing a dungeon on his own and yet he fucking walks away?! Pre this rancid version of Sung, I found him rivaling being weak and relying on others to have potential, yet I already knew that I was going to be disappointed. In episode 1, he destroys all character potential after never admitting that what happened was his fault. He decided to press on yet it was apparently Mr. Song's fault. They even have Mr. Song apologize to Sung despite the fact he now only has one arm and was only making it fair to everyone to have a say in what they did back in the dungeon.
Another issue I had was the very predictable writing. If you've seen enough stories like this one you can see everything coming from a mile away, they even employ the same "tension building" trick twice. (Having the instant teleport stone taken away.)

The direction felt all over the place as well, with scenes about characters we don't know or care about yet getting screen time in really awkward moments. Some are employed for the duality between the two people's lives at that moment but that's not many. The interesting concepts they try to employ, actually scratch that. They don't really try justifying Sung as a murderer other than "it was self defense." There is no moral dilemma, even if the person is a murderer most people can't just simply kill with no hesitation. Take, and I can't believe I'm giving positive notes to Sword Art Online Season 1, but even Kirito gave a murderer the benefit of the doubt since he had the trouble of taking a human life unless necessary. Yet only when backed into a corner of kill or be killed, and even protecting someone he cared about, did he murder. That's interesting, that's drama. Sung immediately kills someone with zero flinching or hesitation. He isn't even doing it to protect someone he cares about. He had given almost zero attention to Jinho who also could have died. He hardly seemed to care about whether Jinho would side with the murderers. This was not cool, this was not interesting, this was literally just murder with zero restraint. Another thing I'd like to add regarding Sword Art Online, the two can be put side by side on multiple scenes where the main character is backed into a corner. Now, bear in mind that somehow SWORD ART ONLINE makes these scenes look dumb. Sung goes into an S-class dungeon despite the fact he's probably a B rank. This was by his own volition, nothing had ever indicated he needed to challenge this dungeon now or never. His mother is in a coma, not on a path of death. His key he unlocked had no given expiration date. Yet he still goes in there and almost dies, the stupidity is palpable. I put this scene next to the fight in Sword Art Online where Kirito, Asuna, and Klein are trapped with the Blue-Eyed Demon in episode 9. Why were they stuck? Because they couldn't sit by and watch people get slaughtered due to someone's arrogance and lack of care for others' lives. That creates tension for not only characters we know and care about (maybe.) but also created a reason for them to be backed against the wall. Sung does this same thing but because he wanted to. And as a final little thought, I'd like to say that Kirito and Sung literally have the same fucking saying when backed into a corner and try to surpass their limits, "Faster. I've got to go faster." Needless to say a small little note, nothing more. All in all, Solo Leveling genuinely was bad, really bad. Why do people love this so much? I've narrowed it down to "turn my brain off and live vicariously through a bland character that does cool things. I don't question at all the how, why, or anything outside of the bare surface of storytelling."