Aliens would die of old age and starvation long before they got even close to earth.
Even if they could get here in a reasonable amount of time once they saw how we run this planet they would turn around and leave as fast as they could.
Once they got away they would tell their authorities to quarantine this planet for fear that the INSANITY was communicable!
One theory that would preclude aliens having to fly vast distances is the idea of “portals” where a craft could simply pass from one area of the galaxy to another far away. In the accounts of the infamous Skinwalker Ranch, the UFO’s were reported to disappear into openings in the night skies through which blue daytime skies were visible.
Having said that, my own supposition about UFO’s at this time is that they may be a type of demonic deception.
You are thinking 3-dimensionally.
The thing about aliens is they are alien - who told you what they can and cannot do?