Revealing your existence to alien species could be one of the dumbest mistakes you could make in the universe. Especially when our technology is not even capable of interstellar travel. Thus any species that comes to visit us will be more technologically advanced. If they are more advanced it likely won't be by 10 or 100 years, but possibly one million years or more.
We would be sitting ducks. There are many ways this could go badly:
- They could be so advanced as to consider us a useless nuisance. They could treat us the way we treat ants.
- They could be inherently nice and rational (by our standards) but correctly see us as a threat to them as our technology advances in the future. Our tribal tendencies (culminating in war) are on display constantly. At best they would just keep their distance. At worst they might wipe us out for their own self preservation.
- Even a benevolent species could be disastrous for us if they transferred technology before we were ready for it.