[panglott]

Yes, the grammar of Japanese has a very simple internal logic and is easy to learn, although quite different from European languages.

The problem is all the words, and there are no cognates.

[tragomaskhalos]

Exactly. The claim that Japanese grammar is very difficult seems bizarre to me because the morphology is so regular, and I don't subscribe to the idea that flexibility and omission of words makes it harder either, more that you just have to attune yourself to it. No, the elephants in the room are (a) the vocab and (b) Kanji.