You're missing a vital point with FMT, diet.
Any FMT is only as good as the recipients follow on diet. Feed the bacteria incorrectly, they die, and back to square one. Borody couldn't control his recipients after they left the lab, its up to each individual to look after what they were given!.
Correct diet is genome dependent. No use feeding cells high levels of sugars if your DNA origins were from North Pangaea. Feed a cell the wrong food for its true DNA origin, its going to die prematurely. Creating additional toxic cellular waste burden.
Then, subject a naturally slow detoxifying genome to toxic burden from increased internal, and external environmental toxicities, and cells are going to become sick and die. Creating yet more toxic cellular waste for an already overburdened, slow detoxifying, genome living in the wrong conditions.
At this stage, accumulated toxicity (Not just metals for those who only consider metals), begins to show as symptoms and causes further cellular damage, from direct, and indirect poisoning, via blockages to so called 'pathways'.
The direct poisoning and the blockages, cause further weakening the struggling genome trying to live in its unsuitable conditions, and pathogens, viruses, wrong bacteria, parasites etc move in.
At this stage the body begins to shut down, putting some folk in their beds, and other not so fortunates in their coffins. Apparently illness is a warning (pretty obvious really). Those who don't heed the warning (symptoms), and take a good look at the basics do so at their peril. Many choose to follow this course!
Note, to those who think toxins are only heavy metals, take a look at the forever growing list of what can now be tested for at a cellular reactive level.
https://www.igl-labor.de/en/service/online-services/iec-selection-tool
The labs don't create these for fun. Demand is there from those who are aware.