I understand your frustration and disappointment.
Thankfully we have a lovely little beach in my neighbourhood where the kids and dogs can run right into the sea and play.
We have sea snakes, little rays, tons of crabs, snails, sea cucumbers, etc etc that we can enjoy watching. This is one of the few places on the island where the land crabs can enter the sea to lay their eggs.
Some of the neighbours did dredge and you can see the repercussions of these actions when we get big seas! Wow, the waves are incredible and when they hit the nearby seawalls the spray is amazing. The damage of beach erosion is guaranteed after big stormy seas.
I think that many of the non-fulltime-residents that put in sea walls either did it because of a misguided belief that it was necessary to avoid erosion, or because the neighbours had put in walls so they had to continue the wall or receive the brunt of the damage when the seas energy is directed at the path of least resitance.
Because we have the turtle grass and shallow depths near the coast the dredging goes hand in hand with development due to the the need of delivery of construction materials.