I'm sure there are other forms of life out there. It may just be rare as the conditions have to be just right and stay that way for a long time. We now know of thousands of exo-planets and in some cases we can tell something about the conditions on them. We could potentially spot signs of life, so could others spot that we are here? We have been transmitting radio for over a century, but that will only have reached our local galactic neighbourhood. If other civilisations have been around for longer then we may pick up their signals.
As for actual visits, that seems unlikely unless they have figured out faster than light travel or they are prepared to travel for generations. Our Voyager probes have only just left the solar system after decades.
But still the reports of strange objects continue. Contact with actual aliens would shake things up. If they wanted everyone to know about it then governments probably couldn't stop them.
As far as other species are concerned, we really need to stop thinking in terms of what we believe to be true. There are things on Earth that can survive in the most unbelievable environments, so finding something that can live on a non-oxygenated planet, for example, would not surprise me. It could well turn out that there are vastly different 'spark of life' species out there. 👽
Yes there are extremophile species, but I'm sure scientists looking for life elsewhere take that into account. We only know of one planet for sure where life evolved, but it could happen in other ways. All life here is based on carbon. Maybe it could work with other elements, but it comes down to chemistry.