Parks are places that are shared between all members of
the community.   You should no more force somebody to
avoid piles of your dogs' poop than you would leave
piles of garbage in the park.  It is unsightly and 
smelly and messy and people can accidentally step in it.
This is not fun.

It is very simple to clean up after your dog, however.  
Since you can watch when your dog poops, you can pick 
it up and throw it away right then and there.  If you
don't then it just sits there like a time bomb waiting
for somebody else to step in it.