I've just finished my first game on deity with the new mode as Gaul. I had golden ages the whole way through, something that I've never been able to do before outside of this mode.
Getting a classical era golden age felt easier, but after expanding early on, staying out of a dark age in the renaissance and industrial eras was a real struggle and earning enough era score became a major focus. It forced me to alter my play style and added tension to the game at a point where I normally would have been able to sit back and relax a bit after settling most of my cities, so that's a big plus for me.
I had fun using the new golden age policy cards. I'm not so sure losing dedications is a strict improvement, but at least it mixes things up. In the base game, I like that dedications force you to make a decision and stick with it for a whole era. In picking one option, you lose out on the other options. They are a nice middle ground between Civ 5's social policies, that are fixed for the whole game once picked, and the flexibility of Civ 6's policy system.
I've yet to experience a dark age in the new game mode though, so I'll need to get a better feel for those before I comment. Overall I had fun with it though, and I'll definitely keep it on for my next couple of games!