The Devs don't need a Dislike button to tell them what is or is not a good idea. The devs take suggestions no matter how big or small and they debate on them. They aren't going off forum majority.

Also number of likes can still serve the same purpose. Scenario: Two members have opposing oppinions Person A has X likes and Person B has Y likes. Whoever has more is obviously popular opinion. People just gotta learn to like what they agree with.