I mean, sure, if you exclude the most complicated writing system currently in use in any natural language, Japanese is simple. I hear Chinese is really easy too if you just do everything in pinyin.
Right, sarcasm off. Yes, the grammar is pretty simple. It has a mere three irregular verbs. The inflection can be somewhat unwieldy (温かくなかったら atatakakunakattara, if it were not warm) but it is nowhere near as complex as European languages.
But. You can’t just dismiss kanji. They are the essence of the language and, counterintutively, are what make it easy to read in long form. A stream of hiragana is almost illegible; you need the kanji to be able to pick nouns and verbs out. And outside of very limited contexts, furigana (phonetic transcriptions of kanji) are rare, so you need to a reasonable command of kanji to get by.