You can throw the baby out with the bath water if you want, but it is clearly not that simple. There is obvious value in many things discussed here, as there are throughout the diet and supplement world, but at the end of the day it is simply a hedging of bets and a crap shoot, sometimes more so than others.
I mean we know many environmental pollutants and toxins (especially man made ones) can cause cancer, at the same time it can also be clearly genetic. Sometimes changes in habits and diet is clearly going to help some where the issue has been influenced by environment, then other times it is probably going to be no help at all. It is also obvious that there are many different cancers with potential causes, grouping everything as 'cancer' is clearly a bad generalisation.
If you got cancer you would not worry about the potential benefit from adding a ton of micro nutrients from good fresh vegetables, adding fresh garlic/ginger/spices, anti-oxidant fruits, certain mushroom species? Just because this does nothing for some people, it is crazy to think it does not have potential, in the least to help you deal your system deal with conventional treatments and prolong your life. I would be changing my diet, adding all types of different things, probably a few choice supplements; maybe I still die and the guy living off maccas makes it, shit happens.
B12/methylation has basically saved my life, but my history and hallmarks, in hindsight, fit this profile more so than others. While others with different onsets methylation probably has no relevance at all. We are all here due to similar symptom sets/experiences, which more often than not is incredibly similar, it does not mean our onset and cause is actually the same.
Chicken and egg, work it out for yourself, or do your best; which is all any of us are trying to do.