Most dog owners are doing their best. Shame doesn't change behavior. What helps is understanding the actual mechanism.
The watershed you live in
A meaningful portion of urban bacterial load has been traced to pet waste through DNA source tracking.
What happens to uncollected waste
A single gram contains ~23 million fecal coliform bacteria. A 50-pound dog produces three-quarters of a pound a day.
Specific local impairments
Murrieta Creek, Temecula Creek, Lake Elsinore, and reaches of the Santa Ana River are on California's 303(d) list for bacterial indicators.