Your scenario only works if drug resistant bacteria won’t kill more people in the future than we could save today. The hopeful solution is that medical science will catch up and be able to deal with resistance. There’s no reason to let people die today for a theoretical, but let’s not stick our heads in the sand.
Anti-biotic resistance is from people pumping massive amounts of drugs into animals for food in factory farms, not people being saved from dying from a small infection and “stopping natural selection.” It will probably become a huge issue. Fortunately, since drug companies have stopped researching anti-biotics for lack of profit incentive, if we achieve socialism we should be able to solve it.