Not all the excursions are as advertised. After my first cruise, I learned I had to read between the lines of excursion summaries. This still doesn't guarantee excursion happiness. For the most part I've been happy with my excursions.
It sounds like you told someone on the ship about the excursion. You might want to contact someone at corporate and give them feedback. Excursion companies are contractors of the cruise lines and I would hope that if enough people complain a cruise line would reevaluate doing business with them or offering that excursion.