tbh even we develop plans, nuclear pulse engine, or smaller light driven craft.... we find now planets in our galactic vicinity and the super-earth planets show great potential.
we may get there at some point but we first need to proof we can successfully manage a planet in a long term otherwise history will just repeat itself elsewhere.
but one fundamental argument vs anything outside our galactic group is the physical limitation of light-speed. real tough evidence. if that falls, some big Einstein laws will fall right down, too. It's not that they don't try, they do, year after year. only to confirm it even more.