This was, simply put, bad. The reason for this is multiple, first, it's technically and musically unimpressive. The instrumentation was crude and would not have stood for itself. The singing was almost exclusively a rezitativ, with dialogue that had that naggingness of constant repetition, without any of the artistic merit.
Then, the story itself simply does not lend itself to the opera. The Monkey King goes on his adventures, one after the other. It's thus quite episodic, as is fitting for a childrens work; the learnings are delivered over time. This requires a fast paced plot, constant introduction of new characters that remain mostly flat and unexplored and are primarily plot devices to move the Monkey King along on his quest. This stands in antithesis to most classical operas: A cast of four to six characters, each with their own motivations and a quite simple easy to follow plot, where the music is primarily there to convey a sense of gravitas to these often rather mundane occurings. (Being reductive here; Especially german Opera Seria tends to tackle far more than the usual love triangle arcs of Puccini).
All in all I do wonder how this happens... why do we not produce works at the scale of before any longer. is it that we simply can't? Do we not educate our playwrights and musicians in the same manne... or is our civilization at such a point of exhaustion that all we can do is throw all the remaining pathos into developing the techne required for what comes next. Oh well. We mustn't despair.