I started it for two reasons. First there is close to no easy to read content when you begin learning Japanese and there is demand for such thing.
The second reason is to see how far I can go like this. It is a sort of thought experiment like you say in your comment.
I discovered after I started that Hans Ørberg something similar for Latin ( https://en.wikipedia.org/wiki/Hans_%C3%98rberg ). His Lingua Latina has been quite influential.
You can see sample pages here: https://omgjapan.com/products/minna-no-nihongo-shokyu-1-hons...
It is 100% in Japanese, but it has a companion book with translated grammar notes if needed. The majority of the book is excellent content in the form of dialogs and readings designed for beginners. I suppose the exercises work better in a classroom setting...
If you know the alphabets (that is kana), you can try the easiest graded reader such as [1] and progressing from there. It assumes little to no grammar knowledge and comes with illustrations and narrated audio that you can follow along.