Trying to claim something doesn't work by doing it wrong is near enough the definition of a straw man argument.
Okay then. I admit it works as long as we feed unrealistic punches.
For example, punches that fast and straight are likely only to come from a trained fighter. A low percentage opponent unless you are training for the ring. An angry or adrenalised opponent will throw big shots with total commitment, giving you body weight and recovery time to work with.
If people prefer to aim low and train to defend against untrained people, like KPM's drunk uncle Ed, that's their
prerogative, but it should come as no surprise when what they spend 90% of training time on doesn't work against someone with half a clue what they're doing.
Sure, many things can happen in a fight, but I've not seen any situation where automatically springing punches happen. Have you?