Written Japanese uses a syllabary - the symbols in katakana and hiragana represent individual syllables.
Of course, Japanese also uses kanji, which are Chinese characters. And Romaji, which are latin letters.
Japanese is, in truth, a holy mess.
Your description of the current state of Japanese writing reminds me of the ancient Egyptians. Hieroglyphics contained all three elements.
Before I went on vaca in Japan I learned katakana, hiragana and kanji.
Came in very handy when driving in small towns. No Romaji there.