Yeah, like it's not that long. They should add that disclaimer to the safety messages at the beginning of the flight. "In case of an emergency, you will have 12 minutes of oxygen, which while we know is not that much, is better than to die instantly."
It only needs to be long enough for the pilots to descend to a safe altitude.
There is a cloudberg article on a crash due to faulty/expired oxygen generators in cargo. They use an exothermic reaction that produces oxygen. But of a fire hazard. I suppose there is a trade off of how much oxygen vs. fire risk.
Pilots are trained in a loss of pressure situation to reduce aircraft altitude (fly down) until the decompression is no longer dangerous. So even with no mask on, the most you will experience is a short period of unconsciousness.