You're never too advanced in a foreign language to go back to the basics and improve your output. A language is a very peculiar thing. Even if we don't understand every little thing, we can and do advance to higher levels. We don't have to be perfect or to have perfect understanding before moving on. That's a good thing. But it also means we can still improve and still learn by going back to the basics and studying some beginner level material even after we are well into intermediate or advanced levels.
I have the book, Kanji in Context. I just recently read through all the vocabulary for the first 250 characters. There is not a character in that group that I have not seen before. I know all of them. But there are quite a few words that I still need to learn. And I was surprised at some of the readings of those characters. Some have readings which I have never seen before.
I'm sure there are many people who have passed Level 2 of the JLPT and who are studying for Level 1 that think they already know all of the Level 2 material. But even those who have already passed Level 1 can benefit from reviewing Level 2.
Some who read this article may grumble. They hate studying and they remember how they struggled. But there is no reason to hold onto those feelings. Studying material that is below your level is not hard at all. It's a breeze! And you can gain from it in a painless way.
It seems to be commonly held that reading for pleasure requires 95% or greater comprehension. That means you should read something where you understand 95% or more and you can still learn while enjoying the content. The same goes for studying. If you understand most of it, it won't be difficult but you can still learn what you didn't know.