> I don’t know. Maybe a little.
is not the right way to interpret the null result (insufficient evidence to reject null hypothesis that it has no effect) because the prior for supplements that people are trying to sell you is so low. In the absence of clear, strong evidence, you should assume the the whole thing is just an example of motivated reasoning. People want nootropics to be real, and other people really want to sell you readily available powders by claiming they have nootropic properties. In that environment, they were always going to trying to concoct a similar narrative about some supplement, and it just happened to be creatine. Those efforts were always going to result in a handful of "positive" studies that turn out to be non-reproducible, maybe because of p-hacking, maybe because of publication bias, maybe because of outright fraud. This is what the literature always looks like for stuff that just doesn't work. If it did work - if the effect size was large enough that you could personally detect it in your own life - then the papers would be trying to put error bars around the effect size, not trying (and failing) to barely distinguish it from a placebo.
“If your experiment needs statistics, you ought to have done a better experiment.” - Ernest Rutherford