Extreme ratings are part of the process. It is taking the average of all votes. So even every vote is extreme it will make an average point around somewhere logical.
There should also be some more complex logic in play but, in general the system will need lot of data to calibrate
It's really interesting how complex the topic is. Fake ratings, extreme ratings etc. I'm beginning to understand why there is no demo yet.
Everybody has his/her own preferences which lead to errors in the rating process.
If you look at politicians, for example, you will not give a politician a good rating if he represents another ideology than you believe in. To overcome this issue the devs should do their best to remind the people that they should be as objective as possible.
Another thing is that you have to consider what the aim of a rating is. Ratings for people or crypto projects are always biased. Look at Cardano. Some people say it will replace etherium in the near future. But others don't agree with them. Some even say that they are scammers which isn't the case.