You are right to promote vitamin C but not as a "cure all". I am sure that you know that Vitamin C is a regenerative. That is that Vitamin C can actually regenerate several other vitamins.
Here is a good example: High EPA/DHA fish oil can go rancid over time. Just add a bit of ascorbic acid, shake well, and it is rejuvenated.
The body uses vitamin C to restore and rejuvenate other vitamins, especially some of the B vitamins. The body can not make vitamins but in some cases, it can rejuvenate ones that have been "spent".
In this point, vitamin C is extremely beneficial. It, however, can not cause a broken or genetically defective metabolic pathway to mend.
I have taken significant amounts vitamin C throughout most of my entire adult life and I know that I have benefited form this but, it did not eliminate my parasites, or my frequent colds and flu ( it did make them more tolerable), it did not eliminate my allergies, or my sleep apnea.
I am absolutely pro vitamin C but know that there are things that it does not cure.