"The WTS explains the situation on earth like a court-case. They pretty much say that it would not make sense for Jehovah to produce other life on other planets, until this case is settled. They pretty much say that if there were perfect life elsewhere, then there would be no need to make a provision to bring us to perfection to settle the case."
That is no argumentation which is used by the WT, so it quite simply is not correct ;-) . You mix up some points. They leave it pretty much open if there is life elsewhere. Or, on the other hand, they say that it is 100 % sure that there IS life out there - because there are angels and other spirit beings. But, when it comes to plant or animal or whatever life forms on other planets, they doubt it - but state that IF there is, it will not change the fact that there is a Creator etc. No reason to panic, no home run for Darwin. If - although it is unlikely - there is life on other planets, God created that life too.
But Earth will forever be the Jewel of Creation, the planet to hold a special position, because this is the planet upon which God's Son, Jesus, gave His life for us. And in so doing, he also proved for all eternity and for all the Universe that rebellion against the Creator is wrong and will be punished, so God's supremacy through Him sacrificing His life has bearing for all the Universe. Not only will such a sacrifice not be necessary any more here on Earth, but it will not be necessary in any place in the Universe. Wherever rebellion takes place - one will be able to point to our Earth and to Jesus' sacrifice and thereafter settle the question. That is the stand.