I've only read checks list 64 chapters of Solo Leveling so by no means can I talk about the whole manhwa, but I think the reason why I'm a bit disappointed by it is that it's good and could do so much, yet doesn't. It feels like the best OP protagonist story out there, and while it has a lot of tired tropes in it, I do think it makes the best usage of it. But... I feel bored by the story sometimes. Scratch that, a lot of the times.
The action looks amazing and I'm gonna keep reading because of the art, but I don't feel the weight of it, if that makes sense. I feel like I'm looking at really good art, not that I'm looking at a manhwa with a story. I don't feel like I'm looking at a character sometimes, at someone who started from the bottom and has kept going and going, who continues to grow. I feel like I'm just looking at another OP dude beat shit up, devoid of any meaning, and that stopped being entertaining for me pretty quickly. It's good, and again I do think it's the best in its subgenre, but it's far from perfect. I guess if we define "perfect" to mean the best of it's niche, then yeah it's perfect. But is it the best manhwa I've ever read? No, not really.
If you enjoyed Solo Leveling I think you'll really like Omniscient Reader. It's take on an OP protagonist is really interesting imo, with a lot of strategy but also a lot of fun action. It's also free on the Webtoons app.
https://anilist.co/manga/119257/Omniscient-Reader/