So this is essentially the equivalent of teaching only hiragana for years and then immediately throw you into the deep end expecting you to suddenly know all the kanjis already, without any transition of gradually accumulating the mapping of morphemes to phonemes.

It seems to me that this ITA would have been quite useful had it served an annotative role taught in tandem with canonical spellings to build the morpheme-to-phoneme mapping. Akin to kana rubytext for kanji in books targeted for younger learners that are then elided for adult readers.