We can conceptualize problems as discrete units to be solved and enumerated. But reality is dynamic and relational, and all problems are ultimately interrelated somehow. It's that true discrete problem units are smaller and simpler than the whole. But this increases the overall work needed.

An example is sequencing the genome. This problem was solved much more quickly than anticipated due to advances in computer processing power. But it also revealed a huge new problem space of epigenetics. Complexity is emergent, not static and hierarchical. Progress is a tree, not a ladder.