I'm both a McCartney fan and a classical music lover and I had high hopes for this, and the opening few minutes are promising. But it quickly descends into a rhythmic mish-mash with a core theme being nothing more than a descending scale sung at a quirky pace. It would work wonderfully in a song as a great hook, but I don't think Macca quite gets the developmental aspect of long works like this.
One of his failings in this, the Oratorio and Standing Stone is his use of his own words. They're simply not very good, and they distract. I suspect that if the Liverpool Oratorio were sung in a language I didn't understand, I'd love it. As it is, it's painful. The same with the end of the (otherwise wonderful) Standing Stone, and with this work.
Yet listen to Working Classical and you can see that McCartney's ear for a melody works wonderfully when engaged on shorter works such as 'Leaf'.
The best classical composers had good editors, people who would say 'this doesn't work'. I wonder if this piece went through an editor? It's promising, but it doesn't deliver. A real shame, but one for completists (like me) only.