One of the biggest problems about this issue is how everyone seems to respond by -- well, by the title of the thread, or some such, ie by this idea that, "clearly", the Oscar Nominations are entirely meritocratic, and so "clearly" adding a black actor would be mere tokenism, and clearly therefore it's their own fault for not being good enough.
I find this suggestion fairly troubling. It seems fairly naive, for one thing. Pretty much nowhere in the world is ever truly meritocratic. Personal connections, for example, may come into play, ie often who you know is just as important as how talented you are (if not more so); or even personal assessments about character, likability etc. Character judgements are often based on very quick, even subconscious processes, and certainly are not meritocratic in nature.
More importantly it is, or rather should be, seen as an utterly false dichotomy. Skin colour is absolutely no indicator on its own of talent, be it acting or any other skill. From which, it follows that the number of black actors capable of winning, or being nominated for, an Oscar should be roughly in proportion to the relative population. And, if year-on-year this is not the case, then you should start to wonder why. Your first stopping point on this journey should certainly *not* be "well, they must all be useless then". I wouldn't necessarily want to stop at the "the nominating committee are a bunch of racists" station either. The issue is complicated by other concerns. For example, John Boyega turning in a fine performance in Star Wars 7, but that entire franchise is clearly looked down on from anything other than a technical viewpoint by the Academy (the seven films have picked up 30 nominations but only one of these was for acting) -- so his being overlooked is almost certainly nothing to do with racism but to not being in the right role to start with to pick up an award. Similarly Samuel L Jackson, another fine actor, has received exactly one nomination ever from his 100+ films spread over 30+ years. On the other hand, a lot of these films aren't going to attract much attention either -- as Nick Fury in the Marvel Comics films he's going to be overlooked primarily because of that. (Will Smith is the same -- I can only think of one film of his that I might expect him to have a reasonable shout of an acting award.) So it could be that Black actors aren't being given the roles they need to do themselves enough justice in terms of awards recognition.
On the other hand, you look at films like Django Unchained, a critically-acclaimed film about life in the Deep South of the USA before the Civil War, starring Jamie Foxx, Christoph Waltz, Leonardo DiCaprio and Samuel L Jackson and written by Quentin Tarantino. Various acting nominations, ignoring those from the NAACP and Black Reel awards that are specific for black actors, were divided up as follows: Waltz 18 (winning 8 including an Oscar), DiCaprio 6 (winning one), Foxx 2 (winning none) and Jackson 1. Kerry Washington, the lead actress, got no nominations other than from the NAACP and Black Reel. It will probably surprise nobody based on that information alone that Kerry Washington and Jamie Foxx are black actors, while Christoph Waltz and DiCaprio are white. This is not to disparage the undoubted talents of Waltz and DiCaprio. But one does wonder why so few accolades went to the (black) leads in the film. (I haven't seen the film, so it could also be that Jamie Foxx was genuinely rubbish in it.)
There are certainly plenty of talented Black actors out there, but for a host of reasons they seem to struggle to get much mainstream awards recognition. It isn't necessarily deliberate, bona fide, "black people are useless" racism -- more, a system that ends up making it that much harder for the genuine talent to get as much recognition.