An acceptable English translation to your French example would be "something needs to be done...". As for the Turkish example, "a good politician" could be needed in the speaker's country or in another one (the speaker could be watching the news of some events that are happening in a different country or state). There is no clue as to which state he/she is talking about (hence the passive voice)! When you say "we need" (active voce) it becomes personal (to his/her country, region, or any place the speaker/s is politically involved with).
So if you were discussing politics at a dinner table, it wouldn't be unlikely that someone said "İyi bir politikacı lazım"? Because if that is the case, "we need a good politician!" is a fine translation. It might not be a direct translation, but the meaning is the exact same.