Here's a video showing Brad Lancaster's permaculture house in Tucson, AZ:

https://youtu.be/KcAMXm9zITg?t=1715

I linked directly to a spot showing him getting good water pressure with only 2.5 feet (less than a meter) of head.

In other parts of the video he talks about filtration. You can watch the video yourself, it's awesome. I hope it inspires you.

It sounds like the place you lived is not a great example of rainwater harvesting and greywater, like they didn't really know what they were doing and cobbled together something mediocre. Do you think that water issues in Flint, Michigan are an indictment against the conventional water system? Or in India? I don't blame you for having a bad personal experience with something and concluding that that thing is bad. That's just how it goes. But take a step back and realize that the questions you have are solved problems. It's just that most people are unaware and many are resistant to change.

The fact that the conventional water system is starting to run out of water in some desert areas, and that the problem is growing, is proof in itself that this system is unsustainable. So we need less pushback and more engaged interest.

Quoting Wikipedia from the Central Arizona Project article:

"The 456 billion gallons (1.4 million acre feet) of water is lifted by up to 2,900 feet by 14 pumps using 2.5 million MWh of electricity each year, making CAP the largest power user in Arizona."

That is not simple at all.

"The canal loses approximately 16,000 acre-feet (5.2 billion gallons) of water each year to evaporation, a figure that will only increase as temperatures rise."

https://en.wikipedia.org/wiki/Central_Arizona_Project