if the issue is the impact of 'bad actors' then it should be handled by using the methods for that, like cloudflare, weeding out dormant accounts, connections from ip's etc., there's no criteria to rank a show and not many people are qualified to be able to do so on all points even if there was. so it's not like a score becomes more meaningful after a drama is finished.
i agree a lot with what LueurArcane said: if someone gets through x number of episodes, drops it and gives an low overall score. as far this person is concerned this drama is finished and i think it's a valid contribution. if i look at stats and yesterday there were 4 people in "dropped" status and today it's 24, i'd take it as a hint, same for score change. so i actually want to see it.
there could be a user profile settings something like "hide score of shows on air" and if it's set it would be hidden just for you. of course if someone starts discussing score changes in comments ... i dont know report it as a spoiler?