My brother and I were having an interesting conversation that sparked a chain of thoughts for me (as often happens in conversation with him). We were discussing the possibility that one of the reasons for the apparent scarcity of intelligent life in the universe (i.e no-one has contacted us yet) might be the existence of a universal bottle-neck on life preventing inter-stellar travel. The argument goes along these lines ...
... The process of developing the technologies required for interstellar travel is so dangerous and carries such a risk of species extinction or even just major cultural disasters e.g. atomic wars, systemic destruction of the environment and the eco-systems required to support civilization that it perhaps only very seldom - or never - occurs ...
If this is the case, overcoming such a bottleneck might require radical shifts in consciousness in an intelligent species. My strong suspicion is that colonialist impulses are unlikely to survive such shifts. What would space exploration look like as practiced by a non-colonialist species?
From this perspective the problem is less one of "interstellar" and more one of "travel". i.e want constitutes "travel". In its simplest sense, travel means going to a place. But we're talking about going to a place and experiencing it. Experiencing it is more than simply a matter of sensory immersion - although this is a huge part of it. It is also a matter of having agency in the destination i.e. being able to manipulate the environment to which you have "traveled".
This means the logistical problem presented by interstellar travel has two parts - resolution, and communication. We have made significant progress with the first part of the problem. We have much better resolution of nearby stars than 100 years ago. We know a little bit about their structure. We even have some evidence of planetary systems (in relation to our own solar system, several probes (including Viking on Mars) have significantly improved our resolution of our own planetary system).
The second problem, communication, addresses the issue of agency. Manipulation of the environment is a fundamental part of "being there" and this is essentially a problem of communication - theoretically similar to that encountered by people experiencing locked in syndrome.
When viewed in these terms, space travel at light speed becomes possible. In fact, the Viking probe to Mars represents a primitive form of such travel. Although the initial journey to Mars was much slower, now that Viking is there, we can "travel" to mars at light speed. Obviously, there are massive technical problems associated with signal strength and bandwidth over interstellar distances, but at least we have identified a spectrum of light-speed carriers, and this seems the sort of problem that may have solutions.
At present we must accept that the placement of an interstellar transceiver to accomplish light-speed travel must itself happen at slower than light speed unless we can establish a communications protocol with an interstellar being that can accomplish it for us. The toolkit one provides such a sub-light speed mission obviously becomes very important. It must be expandable and remotely programmable. One conceivable strategy would be to include organic tools. This has been contemplated with respect to Mars already - the possibility of planting extremophile microbes that would release oxygen into the martian atmosphere, for instance.
It is possible to conceive of far more sophisticated interventions exploiting extremely good use of bandwidth. There may be ways of tackling the problem of resolution that we cannot presently conceive of or are only beginning to guess at. Furthermore, a civilization willing to plan over the 1000's of years it might take a probe to reach its destination is likely to be operating on different planning cycles to us. An intervention might take the form of insertion of particular genetic code into an environment. If this is true, it makes a search for evidence of intelligent design against the backdrop of general evolution rather meaningful. Such a discovery might well yield the information we need to decode a communications protocol and interpret the instructions for setting up a transceiver. We may even be embarking on such a project without being conscious of it.
It therefore seems presumptious to assume that intelligent life is not attempting to communicate with us. It may even be attempting to communicate "with" us in the sense that we are its tool of communication with earth i.e. communicating through us.