I agree with the authors of Rare Earth: Why Complex Life is Uncommon in the Universe, and I also agree with your conclusion. While simple life has likely arisen countless times throughout the Universe, intelligent complex life is probably very rare. Add to that the time scales and distances, and the resources required for travel in interstellar space, and it it obvious why we do not see aliens anywhere. People who believe in aliens visiting Earth often rely on the notion that other civilizations may be more advanced than we are. While that is true, time is still time; distance is still distance; resources are still resources; and physics are still physics.

I am optimistic that we will eventually detect signs of life somewhere else in the Universe. Probably in a spiral galaxy, not too close to the center, around a G type singlet star with sufficient metals, on a rocky planet no more than 1.3 times the size of Earth in the Goldilocks zone with plenty of water and volcanic activity, with a suitable magnetic field, etc etc. Even if we find intelligent life, they will never visit us, nor us them.

By the way, when Earth runs out of fossil fuels in the next 50-100 years, where do you think humans will be going??? The Universe is 13,800,000,000 years old, and humans have had wide access to fossil fuels for only a little more than 100 years. In another 100 years or less, we will no longer have "free" powerful energy. It will soon be clear to everyone that massive energy-intensive projects like sending men to Mars are much to wasteful and costly.

Please see my article, https://medium.com/@chipwoltz/there-is-no-new-planet-f848ab1c3f9d

and for fun

https://medium.com/@chipwoltz/why-aliens-will-not-be-joining-us-for-dinner-384c2d72d9dc