The article isn't about sending humans to Alpha Centauri, it's about sending a probe there. Besides being the nearest star cluster, Alpha's very similar to our own Sun, oh, and I think that's where Spock's ancestors live ;^); Proxima is a red dwarf and the closest of the bunch.
And that’s a great point, it’s too slow for interstellar travel outside our solar system. And this will likely be the case for human for a long time due to the lack of technology available for humans to exceed light speed. Unmanned spacecraft of all types are here for the long term as they have already provided us with enough data to study/analyze for decades to come, far beyond what our primitive manned spacecraft are capable of at this point.