I read this book about 10 years ago and began working on the six progressions. At some point, when when I passed level 6 in one progressions, I would spice it up a bit with other exercises I found in books about gymnastics (eg. l-sits, dips, etc.). Nowadays, I still do the program with some modifications as a way to maintain fitness. I credit it with keeping me healthy and in good shape despite spending hours per day in front of the computer.
I’ve found that while the CC program is great for building strength, it’s good to add in some yoga and cardio. Especially yoga, if you sit around a lot like me.
I’ve also thought about why I don’t see more people doing calisthenics this way and came up with a few ideas:
For most people calisthenics reminds them of gym class. This entails doing as many poor-form squats, pushups, and situps as possible. The idea of “progressions” is not widely known.
Calisthenics are mostly done at home. In contrast, lifting weights in the gym provides not only a ritual (time, place, people), but also a community that can help motivate you to come in regularly, to measure progress against others, to make friends etc. This seems to have some improved with things like r/bodyweightfitness and more pull-up bars/dip-bars in parks, but there’s very little of bodyweight fitness culture.
Calisthenics, even gymnastics, doesn’t reward the user with social-obvious signals like larger muscles or the ability to say “I lifted X pounds last weekend!”. Few people know about pistol squats, diamond pushups, even fewer about planches or muscle ups.
Here’s a video of Larry McEnerney from UChicago teaching about how to make your writing more valuable to the reader: https://www.youtube.com/watch?v=vtIzMaLkCaM
Normally, I don’t watch videos when I want to learn something, but this one made a big impression on me. I’ve found the advice it offers at just the right level—not too low to lose sight of the big picture, but also not too high and abstract to confuse me. The gist of his message is to write with the reader in mind. The video offers advice how to do it, focusing specifically on text structure, which may be your biggest problem now.
Edit: Here’s a link to the handout that goes with the class: https://cpb-us-w2.wpmucdn.com/u.osu.edu/dist/5/7046/files/2014/10/UnivChic_WritingProg-1grt232.pdf