I think you captured the issues well in the last paragraph, but the first thing that comes to mind is a kind of knee jerk ignorance in operation.
The irony is that Westernized versions of yoga and mindfulness almost always REMOVE the belief systems from the activity. Mindfulness is often taught without the Buddhist underpinnings.
…which adds an additional irony. That of people practicing mindfulness in order to ACHIEVE something, or reach some result, which is just about as opposite to Buddhist thought as one can get.