> If ABS can make the brakes not brake even as you fully stomp the pedal - is there a reasonably conceivable failure mode that would simply prevent you from braking despite perfectly good hydraulics and a stomped pedal?

The answer is not simple, as it has changed over time.

Early anti-lock systems were so limited that the system would, indeed, fail to utilize the maximum possible braking force. This was known, and yet these were deployed, because the research said that maintaining directional control, the primary benefit of anti-lock, had greater safety value than the compromise of maximum braking performance.

Today, however, anti-lock is greatly improved, and anti-lock systems are capable of applying extremely high braking force, even to the point of exceeding thermal design limits (overheat) of the brake system components. The sensors are sampling at higher frequency, the braking models are far more accurate and the computers are faster in current vehicles. So current anti-lock can perform at near the absolute limit.

Further, current systems can actually detect panic. Drivers often fail to even use the full braking force available. Current vehicles can detect when sudden, high braking force is applied, switch into "emergency mode" and boost braking force beyond what the driver is demanding.

These features started appearing in the early 2000's. Nissan, for instance, introduced "Brake Assist" in 2001, with the 2002 the Altima redesign (L31 platform) and the Maxima. It has the "panic mode" behavior I've described.

I personally experienced this once about 15 years ago. Somehow I distracted myself, and when my attention returned I was closing with stopped vehicles at too high a speed and too little remaining distance. Collision was certain and my foot crushed the brake: pure panic, and I never let up. I came to a stop in a blessedly unoccupied left turn lane almost aligned with the stopped vehicles. I recall looking over my hood at the driver of the car I'd nearly hit: between us was a wisp of brake smoke drifting up from passenger fender. I could smell the brakes. The anti-lock did that. If I had had no anti-lock, all directional control would have been lost and my maneuver into the unoccupied lane would have been impossible. If the anti-lock had not applied as much force as it did, I would have been in the intersection, possibly getting t-boned.

So they're pretty good today, and I appreciate modern anti-lock designs.