Aside from the fact that aliens from another star system could be millions of years more advanced and have space travel technology we are not evolved enough to even conceptualize, there’s something else to consider, and that is lifespan. If you compare a human’s life expectancy of about 75 years to an insect that may live only a few days or months, the lifespan of a human could be a fraction some alien creature’s exponentially longer life cycle. Therefore something that seems like a huge amount of time for us may be brief moment for some other life form. For example, what if their average lifespan is 250,000 years, or even a million years, whether due to advanced medical technology or simply different biology? Then the journey would not seem so long or unfathomable for them.
I have not seen any evidence that we have been visited(the stuff that passes for “proof” among UFO enthusiasts it mostly garbage,) so I’m not claiming that we have. However, based on what we KNOW about the wide variance in lifespans even within our own meager sampling of species on Earth, the length of time a voyage would take should not necessarily be considered a huge obstacle(for other lifeforms of course, as for us it’s a huge obstacle!)