AMEX MR points were once valued (by TPG IIRC) at 2.2cents/point but IDK if that is true any longer. I can transfer them to Hilton at a 2.6:1 ratio when there's a special but the airline transfer deals seem to be not as good anymore. Your CSR is a worthy competitor and I don't know of many people that would have both. The biggest strike against AMEX at the moment is the travel portal. I have the $99 CSP and I sometimes end up using Chase travel because it works better than the AMEX and I get better point redemptions. However, for long-haul international I still use AMEX directly with the airlines.

As notquiteaff said, 5X on airlines, AMEX offers and the coupon spend (Saks, Walmart, Uber, etc) are the main places you would use it. And now that I have the free Blue Business Plus that pays 2MR on everything I have even less reason to spend on the Plat even if I want MR rewards. However, there probably are people that put a lot of spend on their Plat trying to get a Centurion invite, wanting guest lounge access or whatever. Not everyone is a micro-optimiser.