> […] is completely phonetic […]
… for now in the 21st century. There is no guarantee the current spelling will accurately reflect the pronunciation in the 23rd century.
Pronunication and spelling inevitable diverge over time in nearly any sufficiently widely used language due to languages being living things. People lament the perceived absurdities of the English spelling, yet they do not realise that it is a far more common problem across many languages. Take Tibetan as another and perhaps an even more extreme example where the spelling today is fixed to the pronunciation that existed in the 11th century, a millenium ago. The Icelandic spelling is also very complex and is not reflective of the modern pronunication. French, Burmese and Thai are susceptible to the same problem of varying extents as well. English receives the majority of the criticism by virtue of being more widespread than the other languages that face the same problem.
There are pretty much only two ways to deal with the problem: regularly purge obsolete/changed phonetic rules/encodings from the writing system, which will result in a loss of historical continuity over a long period of time where future generations will not be able to directly read texts written by their ancestors, or keep the spelling intact and allow pronunciation to depart from the spelling in the future.
The only solution that is immune to the spelling / pronunciation dilemma is a logographic script albeit in a different way. The most glaring example is, of course, the Chinese traditional characters. The phonetic quality today is so vastly different from their pronunciation of Old Chinese, Middle Chinese and multiple modern Chinese languages that it is somewhat amusing to see names of historically significant people of the ancient past to be spelled out using the modern Mandarin pronunciation. It is a convention and a common denominator, though.
So the logographic scripts offer a semantic continuity solution to the writing system problem whilst allowing the pronunciation to evolve independently.
Granted, the grammar will also diverge at some point as well but, as the natural language processing (early word2vec, the Bayesian topic model, BERT etc) has demonstrated, the grammatic markers in the writing can be safely ignored to a large extent – at the expense of losing nuances of the colloquial speech. Yet, with a logographic writing system, the semantic meaning and the context will remain largely retained for a far longer time compared to an alphabet based writing system.