There are a few possibilities
1. Flying saucers doing faster than light travel are impossible. No society will ever visit any other. Neither will we. Probable.
2. There are no other peoples that have a rate of increase on any other world, we're the first. Not likely.
3. There are people on other worlds, but over billions of years they are all developing at the very same time as us, give or take a millennia or two. Very unlikely.
4. There is at least one other planet in the universe with alien life that has a positive rate of population increase... and...flying saucers are possible...and...flying Saucers are cheap. If so, Space Aliens would have visited and populated all the other planets a very long while ago, and continuously. Did they occupy our planet and kick the dinos out? No. Then its very unlikely.
5. There is at least one other planet in the universe with life that has a small but positive rate of population increase... and...flying saucers are possible...and...flying Saucers are expensive. (see note) If so, the other peoples will probably never visit most of the planets -- and probably have never visited us. Possible.
Out of the possible, and logical answers, on the whole my guess is that number 1 is the one that it correct, but 5 is also possible. The others are so unlikely that the probability is vanishingly small.
[“expensive“ means that the price is so large that an average family cannot afford a serviceable model for themselves. An expensive ship takes a large government investment in each one. ]