I think they can be worth the time- but it really depends. When I had my first, I didn't take any classes and when I braced myself for the labor and delivery nurse to lecture me about it- she just said "good- then you won't think you know everything". She was the best nurse- explained everything as it happened and educated me in the moment. She could have really forced me into making decisions because I was very uneducated about the process, but she took it more as I was a blank slate and was happy to guide me- and was happy to not have to try to help someone who thought they knew it all from a few weeks of classes.
I did have a bad experience with a doctor after I had several children- who thought all births were the same and fit into neat little packages- I was glad I didn't have him with my first because he was being a big bully about some of the decisions I had to make- even knowing what I was doing at that point, it was hard to stand up to him. If I didn't know anything, I don't even want to imagine what he could have forced me into- decision wise.