New techniques and abstractions is how mathematics expand. Mathematics is about studying structures, proving statements is a part of it but it is not all what mathematics is about. If anything, proofs themselves are a means to an end (understanding). Eg Galois developed some techniques and abstractions to prove that there is no general solution to polynomial equations of degree >=5, but these techniques and abstractions gave rise to whole new mathematical fields.

Mathematics has to be also understood from the perspective of theory building, not just problem solving.