You're exactly right. the metaphor is strained through repeated, unsubstantiated invocations of "ritual, ritual ritual."
Yet only one activity is given: exercising together. The span of rituals doesn't apply to life changes such as birth, puberty, pair-bonding, death, etc. The span of shared values doesn't reach morality, communication, family life, money habits, ecological stance, etc. It's only about time and money for a fitter body.
As far as promoting capitalism? Also strained. yes, you pay to take the class, just as one pays for any activity. That is certainly consumerist, yet consumerist is not always capitalist. There are no activities promoting usury, group ownership, abdication of responsibility through legal entities, or even markets which are features of capitalist society. And these are the features of capitalism we ought to be critiquing. These are its harmful facets. Paying to take part in an activity isn't leading us to feudalism, lifetime indebtedness, massive inequality in quality of life. It's a distraction and underestimation to indict exercise classes when there are real robber barons out there.
As far as "mimics the form of religious services?" I don't see the invocation, offering, the sermon, the reading of traditional literature. Sure there is special clothing and music, but like you say, same with square dancing and, hell, almost any human social activity.
> "often subtly discourages people who are overweight [...] from attending.
Seriously? The entire marketing propganda can be summarized as "get fit!" which implies the consumer is overweight.
I think the author is struggling between making observations and reading too much into things that aren't there without spending enough time in the everyday.