lib_likeable.rb

class ActiveRecord::Base
  class << do
    def self.voteable!
      @voteable = true
    end
    
    def self.voteable?
      @voteable || false
    end
  end
end

like.rb

class Likeable
  validate :check_voteable
  
  def check_voteable
    unless model_type.constantize.voteable?//ну или проверить, если ли у модели belongs_to :likeable связь
      errors.add(:model_type, "This model is not voteable")
    end
  end
end

post.rb

class User < ActiveRecord::Base
  voteable!
end