One Star reviews, IME, are almost always incoherent rants by people with real problems of their own. Two and Three star reviews is where you'll find out where our honest failings lie.
In fairness, sometimes really good reviews are also incoherent rants.

That said, I generally agree with you regarding "review inflation." Anything less than the highest possible number is considered sub-standard, so it feels like the majority of reviews on most sites are either "5 stars" or "1 star" (in order to stand out from the 5 stars, I guess?).
It's almost like there is a lack of nuance and thought put into some of these crowd-sourced reviews.