It would be possible to chart a course for a planet in another galaxy, only to find out its star had already gone supernova before we had even begun our journey. Since, at present, we have no hope of traveling faster than light, we can only obtain distant information at the speed of light, so we would have no way of knowing about the change.
Stars that are light years away are also being viewed as they were as many years ago.
So a star located a dozen light years from here is actually the way the star looked a dozen years ago. A star located hundreds of light years away can only be seen here on Earth as it looked hundreds of years ago.
Although we have a rather privileged view of the Universe as it has been through time, and can see nearly to its beginning, the young Universe we see no longer resembles the Universe as it really is. For instance, before we even begin a visit to our closest stellar nursery, the Orion Nebula, thirteen hundred light years away, it may already have ceased star formation. And at our present fastest man made speed we won’t even get there for at least another twenty eight million years. By that time, any map we’ve made will be long out of date.