I’ll also offer that a reason we’ve never seen a real alien UFO is simply the energy requirements limiting speed of travel through the universe (barring some undiscovered loophole in the laws of physics). To go fast takes lots of energy. To carry enough energy to accelerate takes even more energy. We haven’t even gotten to the slowing down part, the power consumption enroute, and recycling everything and replacing losses (atmosphere, parts, the steady and potentially catastrophic rocks and dust that will be encountered at speed, etc) for the duration of the journey. To cross any relatively minor distance would require decades at minimum if you’re in a star-dense area (now you’ve got to deal with radiation issues assuming the alien biology hadn’t worked out to survive that) to centuries.

You could probably get around that by sending robotic AI of some sort which would eliminate needing conventional life supporting systems, but you’d have to wait potentially centuries to get anything back depending on if you hoped to get a signal or a self-replicating ship to return data.

Yeah. Even if there was quite a bit of life the sheer difficulty of crossing distances in space and the energy requirements make it prohibitive.