Maybe I'm missing something, while the changes are significant, Amex FF earn rates are still better than any Visa card on the market. Granted the Platinum charge card is expensive, but there are significant benefits: travel credit, free night with Accor, status with Hilton, Virgin lounge access that more than equal the annual fee.
1.125 points/dollar uncapped for Qantas/Singapore/Cathay is still best in the market
Devaluations are inevitable, we had a good run for a long time, but it was always going to end this way. The last Amex devaluation was just as significant. We went from 1.5 points/dollar to 1 point/dollar + bonuses for restaurant and overseas spend. It's a game at the end of the day, and as long as you can earn and redeem for more than you are spending (annual fee), you are ahead.