Their points are becoming worthless (Chase has done well in this regard, partnering with United and Southwest), travel booked directly with Amex is usually simple more expensive than other travel aggregators, Costco is dropping taking Amex, etc.
I signed up for a Chase Sapphire Preferred card, and its far superior. Its rental car insurance is first tier/full coverage; I have no need to file a claim with my own insurance ever if I use the card. The rewards are much better, and the yearly fee is only $100.
However, for me the $450 fee is easily worth it. The airline fee credit drops it down to $250. And $250 for lounge access + precheck + Boingo + SPG/HHonors Gold is worth it to me. Without those benefits, I'd be tempted to pursue loyalty to an airline and I save well over $250 a year by price shopping.
I guess that's the crux. Its becoming a very niche card. You have to fit a very specific profile for the fee to be worth it.