App markets (and so many other rating services) are often so dominated by fake 5-star and toxic 1-star reviews, that I think any rating system needs to take the credibility of the reviewer into account.
Any account that only gives 1 or 5 star reviews, should probably have the value of those reviews reduced. A new account created only to give an extreme review of one product, is probably not too credible. Established accounts that give varied and nuanced reviews are more useful and more valuable.
These considerations should go into the calculation of the final rating, as well as which reviews are featured. That way, I think you can discourage fake or toxic reviews and reduce their impact, and focus more on honest reviews.
Amazon does do this now I believe. I've definitely seen products with mostly 5* reviews that have an overall score of like 3*. There's some vague explanation in their help system but they don't go into details unfortunately (for obvious reasons).
This wiper fluid is known to cause expensive failures for rain wiper fluid sensors but it has a cheerful 4.6/5 aggregate rating, despite the numerous 1 star reviews saying the product broke their car.
Sadly that can be gamed too. The fake account can give 2-4 star reviews to randomly selected apps in an attempt to not have it's targeted review devalued.
But it would be useful for normal accounts. Some people are just super-critical of everything. A 1 star review from such a person shouldn't count for as much. Same thing on the other side with people who only give 5-star reviews.
Any account that only gives 1 or 5 star reviews, should probably have the value of those reviews reduced. A new account created only to give an extreme review of one product, is probably not too credible. Established accounts that give varied and nuanced reviews are more useful and more valuable.
These considerations should go into the calculation of the final rating, as well as which reviews are featured. That way, I think you can discourage fake or toxic reviews and reduce their impact, and focus more on honest reviews.