Two thoughts.
1. A 12-mile ruck with collapsing like it's the Bataan Death March is basic fitness.
2. It ultimately doesn't matter if we philosophically "care" about whether a doctor or lawyer can do any one specific task. What we absolutely do and always should care about is that fact that we have standards, and that these people volunteered for this job. No one held a gun to their heads and made them join the Army. They were not conscripted. They made the choice to join the Army, with all that being an Army officer entails. In the immortal words of GEN Bernard Rogers, former CSA:
“This is a volunteer force. Soldiers volunteer to meet our standards. If they don’t meet them, we should thank them for trying and send them home.”
If you're an Army doctor, you take the paycheck. You took the loan payoffs. You'll take the ridiculously generous defined benefit plan. So you damn well had better meet our standards like the officer and leader you're paid to be and that you agreed you would be when you signed on the dotted line.
Whether those standards are the right ones is a different question, and one you don't get to decide at mile marker 11. That's the time to demonstrate that you're meeting your obligations as an officer, not to flail about like some starved prisoner on a forced march from the Gulag.