The only countries/ blocs capable of doing anything don't have an incentive to do so. Those that might have an incentive of sorts, don't really have the capacity. As you point out morality is something of a flag of convenience that is unfurled when it suits us in the name of justifying a decision, but hastily packed away when we decide that the risk doesn't justify the reward. It has always been applied selectively, and in doing so, it can equally be used as a stick to beat governments with in the name of contradiction and unequal treatment through double standards the moment they fail to invoke it. We can collectively wring our hands in angst and even feign moral indignation but the truth of the matter is that different rules apply for sub-saharan Africa. If you look at potential candidates for the job, you can pretty well dismiss all of them for either of the two reasons of incentive or capacity.
If I'm going to be cruel, I'd have to acknowledge a degree of strategic pragmatism exists in the creation of foreign policy. At times it becomes necessary to bend your morals in order to achieve an objective, but there are points over which you don't go. This point isn't static though and shifts. What I'm saying is that you adopt a position in the knowledge that it is flexible, and that you're prepared to bend it, if you perceive the value to be gained from doing so justifies it. In some cases this might involve applying an acceptably low degree of flexibility in compromising a moral stance if it achieves signifcant results. In others it might require significant bending in which case you increasingly have to assess the amount of compromise that you're being required to make, against the value of the results you'd achieve. A classic risk/ reward equation with morality little more than an embarrassed spectator is expendience dictates. Governments are prepared to entertain both scenarios because of the reward on offer, the only that alters is the risk level.
The issue of morality compromise only really surfaces in policy formulation when the reward is perceived to be low, and especially so if the risk is perceived to be high, which would be the case with the DRC. As they conduct a reward assessment governments can sometimes mask their inaction behind morality and say that they're being asked to compromise too much and they aren't prepared to do so on principle etc. What they're normally saying however, is that the risks involved don't justify the reward, but can't actually declare this, so seek to invoke morality compromise arguments instead. What's unfurling in the DRC, as indeed it has in Zimbabwe, is their nightmare scenario, where they're not necessarily being asked to compromise a moral position, but in reality , they simply can't perceive any justifiable benefit for involvement. In effect morality as a justification for a policy decision is laid naked, as clearly economic, strategic or good old fashioned capitalist/ imperialist self-interest hold primacy.
Is it too callous or simplistic to suggest that despite having plenty of mineral wealth, many central African countries don't have oil? Logistically it wouldn't be easy from a military point of view too, given that you'd have some horrifically stretched and exposed supply lines and would need to get neighbouring 'buy in' to launch from, given that the country is all but landlocked.
We have a classic policy nightmare of high risk/ low reward scenario that isn't asking us to compromise any moral position. The traditional response in such situations is to look for a neutral lightning conductor (normally the UN) as this allows us to abrogate moral responsibility and even engage in a degree of blame transference once it starts going wrong. Perversely, countries can even retain a degree of moral dignity in this process by selectively criticising what is afterall, only a nebulous creation of their own global convenience, which is this case would embody guilt. By performing the role of glorified whipping boy the UN is doing its job as it isn't necessary to isolate any one individual country, and so no harm is done to any trade or political relations imperatives that might otherwise be damaged. What member countries are actually doing de facto, is criticising themselves or admitting their failures, but through this global QANGO they're transferring all their moral contradictions to this amorphic creation of their own collective conscience. By having the UN accepted into the collective global consciousness of the world's population as a separate entity, they can scatter the responsibility amongst hundreds and therefore no one has to take responsibility for a problem that every knows they should be troubled by, but don't want to admit that they don't have any economic reason for getting involved with. In this respect the UN performs the role of the medieval anchoress that allows all the worlds nations to dump their intractable problems or inherently insoluable contradictions of conscience on its doorstep. The other approach of course is to create a fog of confusion, where by everyone more or less agrees to blame each other although this invariably ends up with the UN too.
) but please see my last post for my definition(s) of 'tribe', Warbler.