There is more to it than that.
1. As you point out, rail lines are readily repairable. Moreover, the German rail net was well developed, so that alternate routings were readily available.
2. The camps were in the East, in East Germany and Poland. Accordingly, many of them were beyond the operating radius of the bomber forces based in the UK.
3. Bombing accuracy was poor. The U.S. 8th Air Force B-17s and B-24s were lucky to hit large targets (such as steel mills) during the daytime. British Bomber Command operated at night...and was lucky to hit the city that had been targeted. Accordingly, if raids had been mounted on the camps themselves, it was likely that casualties among the prisoners would be high.
4. Finally, a bomb dropped on a rail line in East Germany was a bomb not dropped on a strategic target -- like a synthetic fuel plant, an oil refinery, a ball bearing plant, a steel mill, etc. The latter could bring an earlier end to the war; the other couldn't.
This Pope has a distinct weakness for Left-wing propaganda.
Coincidentally, I watched a NatGeo program on this very subject this weekend. (”Anne Frank's Holocaust”)
Because of the reasons you stated about (not) bombing railways and camps, the allies decided the quickest way to end the genocide would be to end the occupations as quickly as they could.