Commercial growers around here did fine with captan controlling brown rot before these better materials were introduced- but they would respray after every heavy rain and I’m not sure how often they sprayed it when it didn’t. Before my orchard was supplying me with all the local fruit I need I would sometimes buy peaches from local orchards with captan still visible on the fruit. Yum. At least it washes off, but it is sticky.
Protectants require overkill in a way, if that’s all you are using, because you can’t afford the BR to start.