A wise and thoughtful assessment. You are quite right that the techno-fantasies of Elon Musk and his ilk are a giant grift, whose sole purpose is to secure their ownership of everything and all of us, and nature and civility be damned...
How to push back? Not by fantasizing a global mass movement, whether we call it "degrowth" or anything else--that is a pipedream. Rather by starting where we are, in our own backyards and neighborhoods, growing gardens, growing community, and growing awareness. And realizing that "capital" is not just the zero-sum stuff that billionaires like Musk crave--land, fossil fuels, and money, gained by the endless propaganda of "getting and spending" among all of us. Rather, "capital"--that is, available resources for further cultivation--also consists of at least 6 "positive-sum" immaterial and incalculable forms: biological capital (with proliferates with use and sharing, as in sharing seeds and compost); experiential capital (teachable skills acquired through experience); intellectual capital (teachable knowledge acquired through study); social capital (friendships and reciprocity); spiritual capital (inner equanimity and resilience gained through contemplative practices); and cultural capital (useful knowledge and skills acquired from our ancestors). All are positive-sum: the more we share, the more we have.
So, imagine communities living according to a simple rule of thumb (that can be put on a lawn sign or bumper sticker); GROW GARDENS, GROW COMMUNITY, GROW AWARENESS--through learning, teaching, healing, and creating.