AlphaGo is an optimization over a closed problem. Theoretically, computers could have always beat human in such problems. It's just that, without proper optimization, humans will die before the computer finishes its computation. Here, AlphaGo cuts down the computation time by smartly choosing the branches with the highest likelihood.

Unlike the above, open problems can't be solve by computing (in combinatorial senses). Even humans can only try, and LLMs do spew out something that would most likely work, not something inherently correct.