I see what you mean, but it still seems like cancer resistance is a bit "overengineered" relative to what you'd expect from selection pressures. If typical cancer onset were e.g. at age 50 rather than 70, I don't imagine that having much selective relevance in the human ancestral environment, as you'd have raised child-bearing children at that point (and you probably can barely carry your own weight at that point, metaphorically speaking).

OTOH, cancer rate is probably superlinear with respect to error rate, so a small loss of cell instruction robustness corresponds to a disproportionately shorter lifespan.

> if something rips off your foot, that's not an injury, you simply bleed to death or die of infection

That's a false premise.

Plenty of (four-legged) animals can survive just fine without a leg - in fact, it's often said that animals have a spare leg. Some animals might even gnaw their own leg off it's stuck in something and they can't get it out.

It's kind of correlated with size - the smaller the animal is, the easier it is to survive after losing a limb. For a horse, even a broken leg is likely to be fatal.

A missing foot is survivable for a lynx much more so than for a human in the absence of modern medical care.

The same applies for evolutionary pressure in the case of hypothetical regeneration. A lizard can take ~2 months to regenerate a limb, for a human it would take longer simply since the limb is larger and needs to grow more. Prehistoric humans and hominids were calorie limited - if an injured individual is capable and likely to (a) survive for e.g. half a year with the injury and (b) to obtain much more calories than normal to rebuild many pounds of tissue, then apparently there is no strong evolutionary pressure to favor regeneration it as he/she is capable of procreating almost as well even without this feature.