Can one gloss the doctrine of karma as the claim that we are only really hurting ourselves? Can one gloss the doctrine of karma as the claim that we are only really hurting ourselves?
At least in everyday senses of suffering.
Perhaps not including sickness, old age, and death (these seem like counter examples).
But when we suffer from everyday pangs of frustration, due to e.g. frustration with our visual appearance, or lack of wealth (these are just examples).
Thanks for your contribution: looking for the limits of what is and is not our own fault.
Frustration and suffering arise from unskillful intentions. That's bad kamma.

DN33:1.11.154: There are deeds that are dark with dark result.

Harmony and happiness arise from skillful intentions. That's good kamma.

DN33:1.11.155: There are deeds that are bright with bright result.

More commonly, the two are mixed and muddied.

DN33:1.11.156: There
are deeds that are dark and bright with dark and bright result.

However, the truly skillful do not accumulate kamma. They let go of kamma instead of piling it up.

DN33:1.11.157: There are neither dark nor bright deeds with neither dark nor bright results, which lead to the end of deeds.

Looking for the limit of faults is chasing the conditioned, the impermanent and the unsatisfactory.
Instead, look for the limitless in love, compassion, rejoicing and equanimity.