If in current day and age we can create quite good deepfakes. Then what does it take an interstellar alien species to simply blend in and pretend they are humans?
If you take the universe as a whole different species would appear randomly at large intervals, even millions of years apart. So just take into consideration the possibility of aliens that are simply 100,000 years ahead of us technologically, could be more, but in that time frame they surely would have been far more advanced than us.
Just put that into perspective.