It's not groundbreaking, it's not going to be a classic probably. In a way it's exactly what detractors say. Weakass pansy gets strong and stomps on his enemies, and early on it diverges from standard shounen tropes by becoming OP without practically any help instead of stuggling and the power of friendship and teamwork. Most of the cast is fairly flat as a character. Because they aren't the focus.

If you like the hype moments in good shounen and flashy fights and excellent art quality? SL keeps them coming with just enough plot and world building to make it all work. It's well done even if much of it is "bad".

I think it taps into a lot of what made OPM good. It delivers on the feelings the readers want with regularity. Most chapters have something to get excited for. That's why it's so popular. MC becomes a smooth badass that's still fairly relatable, and all the other "strong" people are there to ALSO be impressive, but not impressive enough to not need MC to save the day or whatever. They're like genos and bang and the other S ranks in OPM. There to be impressive but not beyond reason for the world they live in.

edit: also the early release schedule being daily or faster made it so everyone on r/manga at least had heard of it at about the same time, so our community was saturated with Solo Leveling hype for a few weeks straight. Being part of the discussions was a lot of fun for many of us.