You make a great point. To support your point, consider the "FIRE" movement for early retirement, and essays like:
"How I live on $7,000 per year"
http://earlyretirementextreme.com/how-i-live-on-7000-per-yea...

Frugality opens up a lot of lifestyle options. Although even given the $7000 a year, this person seems to have a lot of capital in a sense of goods, education, health, and relationships.

That said, there are a few nuances here.

Self-education is now cheap through the Internet (e.g. watching YouTube videos on how to do math or how to fix things). However compulsory education laws make that problematical for children (although there are homeschooling regulations in the USA that can be navigated, homeschooling is illegal in some parts of Europe). The credentialing arms race also means a lot of corporate-type or professional jobs are closed to people who skip college -- even as there are still other opportunities including subsistence production or small-scale entrepreneurship.

Many common antibiotics are cheap due to mass production. But antibiotics can have complicating side effects from wiping out healthy gut microbiota -- which may perhaps include cancer and depression because part of the immune system and part of neurotransmitter production are involved with the gut. Some other cures for things based around herbs are increasingly forgotten and also require access to a large enough area to roam in to find the herbs.

Most (not all) cancer can be avoided through a whole foods diet and active lifestyle. Such a diet and lifestyle is generally cheaper than the mainstream (especially if you have your own garden). See Dr. Joel Fuhrman's G-BOMBS approach as one example:
https://www.drfuhrman.com/blog/237/g-bombs-the-anti-cancer-f...

But, since it is not all, some people in such communities will, as you suggest, die of things treatable in the mainstream. Also, since the people joining such communities presumably have already been eating ultraprocessed food for most of their lives, they are at higher cancer risk than if they had grown up that way (same with other chronic health risks like diabetes, obesity, heart disease, immune dysfunction, and more that are mainly byproducts of Western lifestyle and Western medicine). So, there are these additional background risks for someone going from the mainstream to the alternative -- but the alternatives may struggle under the weight of treating an influx of chronically sick people. (Of course, many mainstream cancer treatments only prolong life for at best a few months at a great cost in suffering and money, but that is a different issue.)

For good or bad, zoning regulations and pressure from neighbors restricts much of what people can do with their land. And cheap land tends to have issues (biting insects, lack of good water, distance from jobs, distance from markets, poor soil, swampy flooding, fire dangers, distance from other people, and so on). So such "cheap" land may actually be quite expensive in health costs and travel costs and labor costs and accepting various increased risks. The book "Life After the City" explores some of these issues.

Decades ago I read an article (in Westchester Magazine?) on someone who learned "primitive" skills for living in the woods. When asked why he did not go and live by himself in the woods using his skills, he replied that it takes a village to live well in the wilderness. So, an overall issue here is that if you want to live well cheaply (which includes some healthy social interactions for most people), you ideally need to be part of a community with related values.

But communities can have problematical dynamics -- especially when surrounded by another culture that is wealthier and more exciting in various ways. That is why, say, the Pilgrims left the Netherlands. The Pilgrims were tolerated in Holland after the left England where there were discriminated against. But they saw their children and other community members starting to adopt Dutch ways, and the older members also encountered other issues fitting into Dutch society. So some of them decided to go to what was then the remote wilderness in North America -- where they could enforce their restrictive norms on their children and neighbors without being surrounded by enticing "Supernormal Stimuli" and "Pleasure Trap" alternatives (both quoted items being names of books on those topics).
https://dutchreview.com/culture/history/the-pilgrims-in-leid...

Of course, many of the Pilgrims died, and the ones that did not survived in part due to the compassion of the Native Americans (as well as plundered Native graves and so on). And their original collectivist vision of land ownership fell apart in the face of massive hard work and starvation and freeloading in that context. But that is another story.
"Who Were The Pilgrims? This Is The Story You Didn’t Learn In School"
https://allthatsinteresting.com/pilgrims

So, if you really want to be as happy as possible with such an alternative lifestyle, a big challenge is finding a lot of other people who want to live like in the 1920s, and actually willing to do that full-time, and all go to the same place, and somehow can afford to buy the land the community needs. And that is all a big challenge, especially since many (not all) alternative communities tend to fall apart over issues of equity or exploitative social/sexual relationships and so on. Some examples:
https://en.wikipedia.org/wiki/List_of_American_utopian_commu...

While not identical in beliefs, some people have quipped the Pilgrims were essentially the Taliban of their day. And in a way, it makes sense, because to leave behind your home as a community takes some common set of core beliefs and strong social bonds which are often associated with extreme religious sects.

To an extent, the Amish are somewhat like this as far as being tight knit religious-based communities which are apart from mainstream US society. But they still emphasize hard work and related material affluence -- and also happily selling goods and services to the lazy "English" all around them. So the Amish are not quite a community of leisure -- even if many people may find happiness in that life.

So, given that, the Amish are far from what Marshal Sahlins describes in "The Original Affluent Society" of hunter/gatherers who have lots of leisure time since most of the food they need does not take that long to acquire and is done often in a way people think is fun or at least engaging.
https://en.wikipedia.org/wiki/Original_affluent_society

Unfortunately, hunter/gatherers are living in a productive landscape were generally displaced by militaristic bureaucracies wielding mass-produced "Guns, Germs, and Steel" (like how the first century of the US Army was mainly about being used to displace Native populations):
https://en.wikipedia.org/wiki/Guns,_Germs,_and_Steel

Which circles back around to why cheap land to live frugally in community is generally not desirable land.

I do think modern technological advances do make new alternatives possible. "OSCOMAK" is a project I came up with decades ago to help support communities of any size to develop whatever infrastructure they desire (but admittedly it is still more an idea than a realization):
https://www.kurtz-fernhout.com/oscomak/
"The Oscomak project is an attempt to create a core of communities more in control of their technological destiny and its social implications. No single design for a community or technology will please everyone, or even many people. Nor would a single design be likely to survive. So this project endeavors to gather information and to develop tools and processes that all fit together conceptually like Tinkertoys or Legos. The result will be a library of possibilities that individuals in a community can use to achieve any degree of self-sufficiency and self-replication within any size community, from one person to a billion people. Within every community people will interact with these possibilities by using them and extending them to design a community economy and physical layout that suits their needs and ideas."

And like with the Pilgrim/Taliban, :-) I can imagine such tools most useful for a dedicated community trying to "live off the land" in the desert, ocean, Antarctica, or outer space (Moon, Mars, Asteroids, etc.). Those are all "cheap land" (with no or low taxes) in the sense of being generally far away and generally not pleasant places right now due to lack of one thing or another --- including unfortunately other people to form a community with.

See also the book "Retrotopia" by John Michael Greer for more ideas, including how to have "zones" of infrastructure and taxation at different levels that people can choose from.

An alternative to increase leisure though extreme frugality and living apart from society is to upgrade the mainstream society we have, such as with a basic income; improved subsistence with gardening robots, 3d printers, and solar panels; better collaborative decisions making in democratic government; and a stronger gift economy (like sharing information essentially for free via the web like HackerNews for example makes possible).