I think the way you interpret the null result is downstream of considering creatine as "a supplement". You can make the null result say anything by changing your prior about creatine or supplements. That's the issue with priors.

You also seem to reject the possibility that some things help just a bit. The author has another article in the same vein about "things that can help maybe a bit but the evidence we have doesn't really help detecting small effects" https://dynomight.net/vitamin-d/