i have a lot of sympathy for your argument here, genuinely. as you may be able to tell i'm jewish and when i was a teenager, i thought i was an atheist because a) it was culturally in vogue to be that in the circles in which i spent my time but b) i didn't realize that i was speaking a different language from the people i saw talking about their atheism. when i said "atheist", i meant "there isn't a man up in the clouds pointing his finger at earth and zapping rush limbaugh with cancer or whatever", and when they said "atheist" they finished that sentence with "and because all religion holds that as a central tenet of belief, religion is stupid and so are people who follow it." my grandma once said to me "i don't believe in the same gd that you don't believe in" and it didn't sink in at the time, but she was totally right, the atheism i was professing was in reaction to a tradition that i never held. that atheism is what i now call xian atheism, and is held by western protestants who find that their religious tradition doesn't hold room for rationalism so they choose to side with rationalism and cast off their religious tradition. the religion i follow doesn't oppose itself to rationalism, so i don't need to be that same kind of atheist in order to hold on to my rationalism, and so as it turns out, i'm not an atheist, or, i'm an atheist in the same ways that the rabbis i know who are also atheists, are atheists.
the thing is, i think that the thing you're describing is the result of capitalist alienation butting up against millennia of religious tradition and the end result being megachurches is, from a marxist dialectics perspective, simply the way that the contradiction resolves itself. does that suck? absolutely! does that make it not-xianity? i'm not quite so sure. i think i'm pushing back a bit against your taking issue with the use of "xianity" as a metonym for all of the above, because the phenomenon described above has taken pains to associate itself with that metonym. speaking as someone who's a step further outside of all of those dynamics as yourself (you're xian but not into any of the above, i'm jewish but still live in an xian society), while i do know that all of the material factors that lead xianity to become what it has are not inherent to xianity or to religious practice generally, the centrality of protestantism to those material factors makes it really hard to separate one from the other. and not to put too fine a point on it, but the centuries of religious persecution jews faced has been at the hands of more than just the american megachurch types, it includes catholics, lutherans, puritans, russian orthodox, evangelicals, etc. etc. to me, your critique is akin to saying "not all men", but for religion. just as there are good men who fight for feminist ideas and causes, there are absolutely good xians, i'm related to a couple of em, and in no way do i want to minimize your distress when someone denigrates your traditions and beliefs in the course of criticizing american consumerist religious practice, and people who do this are absolutely falling prey to the fallacy of composition. but, the issue they're describing does in fact lie at the feet of (one specific context and formulation of) the religion whose name they're using.
i don't mean any of this as an attack, i'm pretty sure that we both have a common enemy and i don't want either of us tiring ourselves out fighting one another when we have much bigger fish to fry. i also completely understand that my perspective and context isn't one that's shared with every other leftist who rails against xianity in the way that you're describing, and hearing it from areligious or ex-xian people comes across as completely different as coming from someone jewish. for what it's worth, when i talk about this kind of thing, i personally tend to try to append the word "evangelical" to the phrase, because while it's still more expansive than whatever phrasing would be perfectly accurate, saying that the problem in our current context lies in "evangelical xianity" points the finger at a smaller and more specific slice of everything that falls under the gigantic umbrella of xianity.