I'm not against Vitamin D: but my hopes that plausible-sounding claims for its efficacy would prove correct have been dashed many times by new better evidence.
I fit it into that class of supplements, and drugs with mixed study results where it comes down to; is it safe, do I think it might/will work, and if the answer to both is "yes", then take it. Included in that list would be aspirin, glucosamine, minerals, among others, with the latest addition being HCQ/Ivermectin.
Unfortunately for the latter, the western health establishment is trying it's best to block the little people from having access.