If they are bicycle only lanes then I think you have every right to be annoyed at pedestrians clogging them up. Yes I do think that people can become too complacent in a park setting - they wouldn't think about walking in the middle of the street elsewhere would they? It sounds like the pedestrians are putting themselves in danger, not only from bikes, but from cars also. It sounds like your park needs better signage and enforcement, though I doubt you will ever see it. We have very few separated facilities out here, tails are nearly all mixed use. In the places where they are not there is little to no respect from the walkers for not using the "wheels" only parts of the trails for walking and yes they do act as if they cyclists are the parties in the wrong.