I think the majority of people saying there is no life out there does not comprehend the vastness of space. Its actually quite idiotic saying there is no other life and we are alone.
Have we had visitors, That I don't know. Maybe, Maybe not...We simply don't know. But personally I think they have visited earth. There are simply too many cases of people seeing things for me to believe otherwise.
If we look at humans alone, +- 1920 years and technology did not really move that much (Actually many, many more years than this). Then BOOOOM, going from moering a donkey with a stick to get to our destination, to self-driving cars in +- 100 years, I feel there has been some sort of contact and they shared technology with us.
Not saying humans could not achieve this on their own, but looking at history and the pace at which technology was evolving and how it changed in a few short years, it's quite miraculous