Club rides are great.
I love the social component, the camaraderie, and the flying along at a good clip in a smoothly functioning group. I also love not worrying about where I'm going because somebody else has figured out the route.
I get what they're saying, but in my limited experience so far, I think group rides provide the only way to practice very specific race skills. Like:
4. Economical riding
5. Peleton confidence
I respect both authors (and use both books, they're great) but if you consciously choose to do it, you can adapt your club ride to help develop your race skills. You don't even need to tell anybody. Mostly.
Attacks: Like sprints, these can be done on an ad hoc basis, especially on longer climbs where the group tends to break up anyway. Take a jump and see how much distance you can put between you and your pack for five minutes, then drift back & re-join. You may get a chaser or two, which adds to the fun. For etiquette's sake you may want to mention that you are going to try this beforehand, just so nobody thinks you're being a dick and trying to drive the pace up.
Bridging: On rides with a larger group of mixed levels of ability there is a tendency for the pack to fragment and re-group. Again, often on longer climbs or hilly sections. Sometimes when I'm back of a group that has broken away I'll pretend I'm in a race and trying to bridge on to a lead group (or, more realistically in my case, catch up to the ass-end of the main peloton). Occasionally one or two others come along too. What I like about this is the psychological struggle: forcing yourself to hold a higher, painful pace as long as it takes to make contact. And there's something about that last 10 or 15 metres. It seems endless, and it's a pig to get over it – but it feels great when you do.
Next: Riding efficiently, and getting comfortable in the pack.