There is a ole' axiom; "someone who has a bad experience tells 10 people, those who had a good experience tells one person".
Whenever I look at reviews I always disregard the great ones and look at the bad ones - More often the bad ones have unrealistic expectations.
When a vast majority think the product / service is good, perhaps the complainer should look in the mirror........................
A $10 car wash is just that; not a detail job !!!