What's "complete unscientific garbage" is taking a correlation between a dozen self-reported symptoms, and a COVID infection months before, and deducing that it

What's "complete unscientific garbage" is taking a correlation between a dozen self-reported symptoms, and a COVID infection months before, and deducing that it proves the latter caused the former. There are numerous potential confounding factors, and no real science would dismiss these, and claim a controlled and randomized experiment is not necessary before drawing conclusions.