Why not? Problem with believing aliens inevitably exist out there is that there will be all kinds of them. Those that would avoid us and those that wouldn't. For whatever reason we might not even understand. As for ways to travel between stars we can already think of some. Generational ships for example. May take a long time to reach the destination but should work. So maybe the question is why haven't we seen any of them yet?
Because we live in a redneck area of the solar system. We're BFE. There are areas of the solar system where the distance between stars is much smaller. A generational ship would turn to dust before ever having reached us. We can't even solve our most basic problems, what makes you assume that aliens are any better at it?