Why we haven't found aliens (pt 1)

Do we have the technology for detection in the first place? 

Right now we are trying to locate orbiting planets in alignment with the star and the scope, but this has low positioning probability. Our coded messages can reach the speed of light, and it has barely even been a century for us to be sending out messages. Even assuming speed of light as absolute, it doesn't make sense for an advanced species to use same spectrum, bandwidth and encoding methods as us. For any civilization lvl 2 and beyond, they'd be likely to employ Dyson Spheres, cutting of the light that helps us in detection in the first place.

If not so advanced, then they're on the same boat as us. Even on Proxima Century, with our current capabilities, just to detect with the same energy emission signature as our plannet would be impossible. 

I can think of no feasible methods to even investigate the Alien life, much less 'sentience'. So I think it'd be too early to jump into any conclusions.