This is not correct. It's true in the US for prostate cancer, which is one of the most notoriously treatable forms of cancer, but it's not true for cancer at large.
(It's also not true for prostate cancer in many other developed countries, which actually have a worse track record at treating cancer than the US does)
"Half (50%) of people diagnosed with cancer in England and Wales survive their disease for ten years or more" [0]
Since lots of cancers and lots of deaths are in old people, 10 year survival is quite a high bar.
[0] https://www.cancerresearchuk.org/health-professional/cancer-...
Lumping all forms of cancer together is misleading, because cancers have dramatically different mortality rates. You need to separate by type of cancer, or else you're really just measuring the relative prevalence of different cancers.
As it turns out, the UK has a relatively low survival rate of cancers compared to other developed countries, including the US.
https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
I get that this explanation fits with a common preconception of the US, but it doesn't bear out in reality. The US has a higher survival rate for all common types of cancer than all other developed countries, and this has been consistently the case for the last three decades.
https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
As someone who has autoimmune diseases, you must be getting your information from a source I'm not familiar with. Auto-immune disease are a long game of guess, test, and adjust.
Modern medical results would absolutely be viewed as a miracle to someone just a few decades back. Something like 90% of cancer cases are either cured or successfully suppressed (to the extent that the sufferer ends up dying of some other cause). Almost all endemic diseases have vaccines. Virtually no one dies of a bacterial infection today. Even most autoimmune disorders have effective treatments now.
The fact that there are problems yet to solve in medicine, and remaining voodoo in its practice, still doesn't change the fact that we're living in a miraculous age.