This is like saying English is written with logographs, not an alphabet. Kanji are logographs and not a syllabary. Hanzi are closer to being a syllabary than they are to being logographs. The sound is the primary concept.
Obviously, the characters do convey considerably more than just phonetic information. But phonetic information is the first and most important thing they carry.
It is quite remarkable how people continue to believe what their elementary teacher told them, even after years and years' experience to the contrary.
In English, people believe that "Elements of Style" is full of good advice despite everything good they have ever read violating every rule on every page.
This is like saying English is written with logographs, not an alphabet. Kanji are logographs and not a syllabary. Hanzi are closer to being a syllabary than they are to being logographs. The sound is the primary concept.
Obviously, the characters do convey considerably more than just phonetic information. But phonetic information is the first and most important thing they carry.