If cloth masks don't work, they aren't doing much for source control either. They don't magically filter better in one direction than the other.

If everyone was wearing a particulate mask (e.g. N95), source control wouldn't matter as much. Masks with an exhaust valve are significantly more comfortable and comfort is the reason the CDC is currently citing in regard to their recommendation for people not to wear particulate masks.

If your protection plan relies on everyone else doing something complicated correctly, you have already lost. I think controlling the spread of a virus in the general population using source control is not something our species is capable of.