When it comes to political debates, one can either argue on the framework level or the empirical level. On the framework level, discussions revolve around the basic principles that motivate just political systems. For instance, we might ask whether equal opportunity is all that is necessary for an economic system to be just. The empirical level only comes in once we have accepted some basic principles and are trying to determine what political forms actually cohere to them. So in the equal opportunity case, we can have a debate about what systems actually achieve equal opportunity. Thus, we can argue both about the importance of equal opportunity as a basic principle and about how best to achieve it.
In the United States, it seems that most regard equal opportunity as an important basic principle. I think it is worthwhile to challenge that idea, and argue that the goal of an economy should not be simply to generate a hierarchy of talent and compensate accordingly. But it is probably easier to just challenge the empirical assumption that equal opportunity exists presently in the United States. First, we must define equal opportunity in a way that makes its achievement measurable. John Rawls gives such a definition in his account of the typical understanding of liberal equal opportunity:
To this end, fair equality of opportunity is said to require not merely that public offices and social positions be open in the formal sense, but that all should have a fair chance to attain them. To specify the idea of a fair chance we say: supposing that there is a distribution of native endowments, those who have the same level of talent and ability and the same willingness to use these gifts should have the same prospects of success regardless of their social class of origin, the class into which they are born and develop until the age of reason. In all parts of society there are to be roughly the same prospects of culture and achievement for those similarly motivated and endowed.
As I mentioned before, it is completely legitimate to challenge the idea that this is even an important concept. More interesting perhaps is determining whether our society — as rhetorically obsessed with equal opportunity as it seems to be — actually comes anywhere close to achieving this ideal. It doesn’t. No matter your political bent then, if you subscribe to a view that cares about equal opportunity, you should have some theory as to why our present institutions do not deliver it, and at least be open to and searching for reforms that might do so.