Given the size of the observable universe, I think the most likely answer for the Fermi Paradox is "all of the above, and a secret nth thing."

Life is rare, intelligent life is more rare, intelligent technological life is even more rare and inherently unstable, intelligent technological life maintaining political and cultural stability long enough to discover space travel is harder, the actual space travel is harder still, interstellar travel is harder still, the universe is vast, electromagnetic signals diminish into the CMB over time and distance, we may simply not see them, they may simply not see us, they may see us and simply not care. Everything, everywhere, all at once and sometimes you just get sucker-punched by an asteroid or a gamma ray burst or your sun just explodes.

The universe is the most complex and complicated thing there is, and there are more unknown unknowns than stars in the sky.