I suggest you study the River Ganges and then reevaluate your position. Poop alone can destroy a river on the scale of citywide human populations.
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Plastics are actually INCREDIBLE for preventing waste. A plastic bag for groceries is composed of roughly 13mL of LDPE, or roughly 260 "drops" of plastic! LDPE is so incredibly efficient at manufacturing that there's much less waste in its creation than textiles or other materials.
The issue with LDPE is that it doesn't biodegrade very gracefully and thus becomes a pollutant if its disposed of improperly. But from an engineering / manufacturing perspective, its one of the most efficient materials to make and manufacture.
In contrast, a leather bag required you to raise, feed, and then kill an animal. Indeed, the mammoth was likely hunted to extinction by primitive humans, and demonstrates that even at the small scale... humans can affect the environment.
And sure, the leather biodegrades gracefully (at least, more gracefully than an LDPE plastic bag). But you have to consider the environmental costs in creating the leather (water, food, and waste created by the animal before its leather was harvested)
It makes absolutely no sense to "cargo cult worship" the mythical tribeman's lack of pollution, when our society is funadmentally built differently.
There are some incredibly simple solutions available to us that the "Mythical Tribesman" doesn't have. IE: We can pass a law and regulate pollution in our country, if we can convince enough other people that the costs are worth it.
IMO, one of the biggest myths is the myth of the primitive but efficient savage. Its almost always a "obscure tribesman" of some kind, be it a native American, or maybe an African tribesman... but the myth is always the same.
Apply the "Mythical Efficient Tribesman" to real life, and things start to go awry. The mythical Tribesman poops in the river when he needs to use the bathroom for example... if a city of 1-million+ people poop in the river however, it creates contamination and disease... and probably isn't good for the general environment either.
IIRC, the most efficient places on earth, as far as lowest environmental impacts, are generally cities. Cities with central sanitation to clean up sewage BEFORE it enters rivers for example.
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A sustainable economy is about closing the loop, keeping track of trash and doing something about it. Landfills and recycling centers are actually hugely efficient in the USA, especially some materials like Aluminum.
Waste Disposal centers have huge bins for a wide variety of items: textiles, metals, electronics, plastics, paper, oil, bio-wastes... each of which can be efficiently turned into new products.
For a lot of people, simply being aware of your local waste disposal center and their services would greatly improve your environmentalism. Don't throw away old Jeans, send them to the "textile" center to be recycled. Purchase "Plastic 1, 2, 3, 4, 5", but not Plastic 6 (which is harder to recycle and very few centers actually recycle it). Etc. etc.
Know what your city can offer and use their services. You don't need to run your own compost pile, just send your leaves / eggs / food waste to the landfill for it to be composted into mulch.
In my experience: rural areas of the USA have very few waste disposal services... and may even be running local "septic tanks" as their primary means of treating sewage. But even these more primitive means of sewage treatment are far superior to "primitive tribesmen" who resort to effectively dumping their sewage untreated in a river.