Since LLMs are trained on "random people online", why are they not of equal rank?

For me, for now, they are. And being "many random people" and not "random person", they average out into something much more trustworthy than even recommendations from most individuals I know personally.

Operative word is "for now" - LLMs caught entrepreneurs unprepared, but they'll catch up and poison this too, same thing that happened with search giving rise to SEO.

I see LLM as the average of multiple random people and traditional common sense from wikipedia and books.

It's worth keeping in mind that some of those random people are trolls.

In fairness to your point, I also find that Amazon reviews can no longer be trusted, and I really try to buy as little as possible from Amazon. Due to this, and other reasons, I find it quite difficult to have a good sense for whether I've bought something high quality, or if it'll be a piece of trash.

Drifting off topic now, but Amazon could easily implement a few measures to really lock down reviews, but they purposely leave it gameable because it drives sales.