Regarding the concept of aliens existing or not, doesn't it boil down to 3 options?
- We are simply too early- We are the first - this isn't human arrogance, we could be the first
- There are many great filters, including one in front of us which will wipe our existence. This would include the filter of creating life as well- this may be a much harder process then we assume, making life much rarer then we think- we just passed that filter. So if there is no alien life, that would fall in this category
- We are too insignificant to be notice and don't have the ability/technology to notice other life- this may mean when we become significant enough we get wiped out