The overall efficiency of Anaerobic metabolism of glucose is 29 to 30 ATP versus only 2 ATP per glucose.
Anaerobic metabolism is not a substitute for aerobic metabolism. Anaerobic metabolism is a temporary supplement to aerobic metabolism when the need for energy is high. When a short burst of energy is required as in sprinting, anaerobic metabolism augments the effort that can be made. This is a survival mechanism for animals such as antelope that depend on speed over short distances. The cheetah also needs a short burst of energy for survival. Anaerobic metabolism does not produce lactate, it produces lactic acid. This contributes to an acidemia and consumes bicarbonate. It is commonly stated or written that anaerobic metabolism produces lactate which ignores the production of a metabolic acid. Because anaerobic metabolism creates this acidemia the process has to be temporary but that is the need.
In terms of the efficiency of carbohydrate metabolism, glucose is converted to 2 lactate(lactic acid actually) via the anaerobic pathway. There is still energy left in the lactic acid. These are carbohydrates. Aerobic metabolism completely consumes a glucose molecule to produce 29 to 30 ATP.
Oxygen Debt is a Useful Concept
Ultimately aerobic metabolism will have to resolve the acidemia.