I get a lot of casual senior strollers on our river path. This morning there were 2 ladies taking up the whole path, so I slowed way down and politely stated
"On your left."
....
"On your OTHER left."
They then moved over to the right to let me pass.
Understanding shared path etiquette is a shared responsibility. I like to buzz along on a nice day but I slow down and give a wide pass to pedestrians too.