At level 40, I can read most of the manga I’m interested in. As a caveat, I’m mostly interested in dialogue-heavy slice of life kind of stuff. Descriptive narration is significantly harder than dialogue.
And I mean, “reading” is a spectrum, not a binary. I still usually have to look up one or more kanji on any given page. Even when I know all the kanji, they may be in a compound I’ve not seen before. Verbs are particularly tricky because you may see two verbs, know both, but not realize that -when combined- they mean something fairly different than you’d expect.
I’ve never studied grammar formally, but I’ve also got nearly two decades of osmosis (aka subtitled anime) to draw on, so I get a lot of basic things about sentence structure. Enough to work through a majority of sentences without having to stop and go “what the heck?” anyway
At first, kanji was the clear bottleneck, so my grammar gaps didn’t really matter. Just chugging along through WK levels added a huge amount of comprehension while reading. But now I’m getting to the point that grammar is becoming the bottleneck to advancement, and while it’s still really important for me to finish WK, the comprehension gains I get per level will understandably face some diminishing returns.