Ipswich were a goal down at the break, but three penalties after half-time put Palace in a strong position.
McCarthy, who was taking charge of his second game as boss of the Tractor Boys, told BBC Radio Suffolk: "That's highlighted our frailties. It was a sobering experience.
"I've certainly learned a lot. I'll learn even more when I watch it back in the morning.
"There's a lot to look at. It's really disappointing."
Ipswich are bottom of the Championship, having lost nine games in their last 14.