Rating system - Five star problem
I recommend using the Votingapi Widgets module based on the Voting API in D8, it works and does the same as Fivestar.
Some more details about this module (from its project page):

A flexible field based Voting System based on Voting API.
You need Drupal Version &gt;= 8.2.3. (Multiple form instances on a page).

Be aware: only an alfa3 release for D8 as of right now.