As someone whose paid travel is exclusively in Economy & Premium Economy, I agree with the sentiment of the OP, but not really the conclusion.

For upgrades, AM are basically worthless, as you have to spend too much money on higher fare to make it usable.

For full redemptions, AM is decent. I am a Gold member so I get around 60-75K miles per year from flying, plus more from CC spending.

In the last few months I've redeemed an F trip HKG-SIN-HKG and another F trip to North America and back. If I put a dollar value on the same paid flights, it's probably around HK$100,000. I don't think I even spend HK$100,000 per year on CX cumulatively.

From that perspective, I'd say the programme is acceptable, provided that you work on the assumption that upgrades are poor value and the way to get best bang for buck is F & J full redemptions.