Apples and oranges comparison. Go is much closer to chess than it is to recognizing sarcasm.
Good computer chess play is based on a deterministic tree walking algorithm, something that’s been clearly in computers’ wheelhouse since forever.
Good computer go play is based on neural pattern recognition, which is also (probably) what human sarcasm detection is based on.
Conversation doesn't work like that, and takes a vast amount of information to understand whether someone is being sarcastic.
Every tree search algorithm needs a guiding heuristic, and that's what AlphaGo replaces with a neural network.
So both DeepBlue and AlphaGo are fairly described as being based on tree search.