The idea of centralization is not inherently incompatible with the idea of categorization.

And it's really not that hard in most cases. Is it an objective question about writing code? It goes on Stack Overflow. Is it about programming as a broader topic? It goes on Programmers. Is it about servers or systems administration? It goes on ServerFault. Is it about general computing? It goes on SuperUser. Is it a highly subjective question about programming? Stack Exchange is not interested in your question.

(I do agree that SO and Programmers seem more like an artificial division than natural categories, but I still don't find it that hard to figure out whether a question is good for SO.)