Or normalize the ranges between min/avg/max of the ratings given by each individual user to min/middle/max of the scale before merging the number into the total.

If you do it secretly like shadowbanning and introduce it softly by slowly blending between conventional score and normalized, it would drive a whole generation of SEO/social/share-economy experts delightfully mad. Think of all the free publicity!

Jokes aside, it might help to regard low ratings as what they are: a way to flag bad behavior, dead serious stuff. We should stop pretending that it is a game, then maybe solutions will be more likely to appear.