Yes, phages are the natural "antibiotic"/population control for bacteria. https://humanmicrobiome.info/#bacteriophages-phages
Antibiotics can make phages go extinct. https://humanmicrobiome.info/antibiotics/#virome
Phages were being researched as an alternative to antibiotics, but antibiotics seemed easier and cheaper, so they grew in popularity and use. Unfortunately, antibiotics come with pretty severe collateral damage.
Something similar, that you can (and should) get involved in: https://forum.humanmicrobiome.info/threads/the-fda-and-fmt-regulation-part-2-jul-2024-humanmicrobes-org-i-met-wit.520/#post-1370
"It wouldn't surprise me that improving people's health this way actually slows down the ageing process,"
Then you may be allowing preconceptions and biases to prevent you from processing new and contradictory information.
Your entire argument is climate change?
No, it's not. You should click the link.
Nonsense. That's an extremely ignorant statement. The current population level has been doing massive damage to our planet. https://github.com/MaximilianKohler/Archive/wiki#some-of-the-major-problems
largely to no avail
Great news. It's insane how few people seem to care about the damage occurring from overpopulation.
General poor health has been increasing. Obesity rates and rates of lots of other conditions have all been increasing. It can't all be due to microplastics.
Think they would be able to make some sort of artificial FMT
We're a long way (many decades) off from that. This blog goes into more detail with references: https://www.humanmicrobes.org/blog/stool-donors-one-in-a-million-ai-funding-potential
One of which is this page that shows the severe limits of current knowledge: https://humanmicrobiome.info/testing/
More antibiotics is not the solution. We need to be moving away from antibiotics, and drastically decreasing their use/overuse.
Keto is an elimination diet. If you need it, it means you lack the gut microbes required to properly digest other foods.