They can have a fine although not amazing Faith economy by quickly building Holy Sites once their oppidae are built. Yeah, there's a population restriction, but they overcome it in time, especially if you are clever enough with city placement not to go into solid Hills. And all those dicey RV wonders that take forever with RV civs are easy peasy with them. Notably Hagia and Meenakshi. So they have reduced opportunity cost there. I'm not saying they are good at it, but better than a civ with no inherent bonus toward religion. C+ is above average, but not a good as Good.