Classical Goldens are essential for civs reliant on Monumentality or coastal civs, since you can usually get harbors up midway through Classical for Free Inquiry. Japan also really likes Free Inquiry Classical Golden because their Commercials are insane. Otherwise, you don't necessarily need it, and a Heroic Medieval can be amazing. It's not often I have enough loyalty issues to make Classical Dark Age a problem. There are usually only a few cities that could have problems and governors fix those. There can be a bit of an efficiency loss in stationing a governor in an outskirt but it can be managed. I'd much rather have a Classical Dark Age than a Normal Age, unless I'm going to war in Classical, in which case Dark Ages can be a bit deadly. Even then, my goal is usually to wipe my neighbor out so a Dark Age can be managed.