First we have those that are willing to share a space and regulate their behaviour accordingly and then we have those people that regard 'their' space as theirs and will not bend or adjust for anyone.
This.
I used to work in an area with a wide pedestrian path, white line separated from a double wide bike path. Trying to use it was a nightmare as people often walked in groups and would do so all abreast, resulting in a move onto the bike path (or worse use both paths) so they could walk 4 or 5 people wide and not give way to anyone.
The opposite of this was one of my colleagues, who would when alone still walk right up the middle of the bicycle section "because I don't like cyclists".
What can you do?
Not a lot to be honest as many people have personalities inherently selfish, controlling or are just plain stupid, or pick any combination.
A white line is not enough, unless fines are brought in, just as they would be if you drove your car along pavements or if you obstructed the flow of traffic by wandering randomly all over the highway on foot. There is no one to police this, no one to impose fines or make laws to create fining opportunities. The next more community based "lets care for each other and co-operate" is for parents and schools to teach children from a very young age to be community spirited and walk/bike in the right places, which would need bike lanes etc to be much better and consistently marked (yes, a miracle is needed), but lets face it, as many parents are in the already mentioned personality categories, education is not going to happen either, just look at the number of child cyclists/illegal electric scooter riders weaving across roads, dressed in black with no lights after dark. The parents don't care about educating children re roads, even if it means thier kid or other people might die or be crippled for life. But then, equally thoughtless cyclists doing 15 mph+ on shared paths instead of moving to a road do nothing to promote safety or consideration either.
I try to use quiet roads rather than shared paths as there is less chance of a pedestrian causing me to become involved in an accident.
Its all rather sad really. It will never improve.