Firstly, I have no doubt that aliens exist,
but…
I think we can be almost absolutely sure that none have ever been remotely near our own planet. The thing is, space is big. Much, much bigger than people really can even imagine. We know there are limits to physics, and nothing allows for faster than light travel. And nothing we can realistically conceive of allows any means to practically bypass it. Sure, wormholes theoretically could work, but even if they could exist, they would be unlikely to be controllable and would require unimaginable amounts of energy to generate or maintain.

I used to watch The X-Files and I genuinely thought that it might be realistic in its portrayal of shadowy government agencies hiding alien artefacts and visitations. Facts and information got in the way though and I had to change my position based on the experts and scientists that clearly knew better than writers of fiction. It was a little disappointing to learn the truth, but I did feel empowered by it.
So many people have rigid ideas they can’t be swayed from even in the face of new or improved information or evidence.

UFOs as a phenomena exist, but that doesn’t mean they are extra-terrestrial in origin. It just means they are unidentified. And often, when held to scrutiny by experts rather than cranks and believers, such sightings can be explained or identified.
It’s no coincidence that so many UFO photos or videos are blurred, because sharp images are usually easily identifiable. Everyone has a camera with them now, but still no decent alien evidence.

Sightings of aliens also most often have them in some sort of humanoid form. That is, walking upright with two legs, two arms, a head with 2 eyes and a mouth in similar positions etc. There’s no reason why all higher life forms would follow this format and it’s pretty clear that people “see” aliens this way because their main source of reference for intelligent life is other humans and other false representations of aliens based on other people’s descriptions and creations of them. Even in fiction, aliens are more often than not basically humanoid as it’s easier for us to think about them, or in the case of film and TV, to create them and act as them. I’m sure any real aliens out there would amaze us because earth’s evolution isn’t likely to be so similar anywhere else.