Ben, it’s a great observation that you start with. I spent some time living in a Thai Wat in Thailand, and so am aware of this contradiction (my book about it, What the Buddha Never Taught, was for awhile blacklisted by the Sangha! But it’s now tolerated because it’s made a lot of people interested in learning more).
I was with you a good part of the way, but I believe you have made one fundamental error in that what Theravada monks consider happiness is not the same as what humanists consider happiness. Further, the cessation of suffering is not the endpoint of Buddhist practice. The Buddha, and all his enlightened followers did not simply retreat into repose…they taught. They practiced compassion. I’ve known some monks who “got” that. Wow, they are amazing individuals. They have attained something. And, the ones I know are both filled with joy, and participants in life.
The thing is, that space is not defined in Buddhism. It can only be experienced by those who take that journey. This is not an arduous path to hedonism…it’s a journey to different and remarkable way of being.
I once tried to explain to an illiterate Tibetan why I did not believe in Buddhism. I talked about some of my disagreements with the doctrines of reincarnation and karma. He looked at me like I was an idiot. His voice dripping with scorn he said, “you don’t know anything about Buddhism then. It’s not about doctrine, it’s about devotion your life to examining experience and seeking answers to important questions. I go to ten different lamas with the same question, and they each give me a different answer. That’s not inconsistency. That’s because they are each working from their own deep experience of life.”
I was humbled by this encounter. I realized that to judge another religion from the outside is to miss the essence of whatever it it really about.