Old filled in pond and sandy soil speculative question.

The property I just bought used to have a large pond. At some point years ago it was filled in. The liner is down there mostly intact. At first I thought I would dig it all up and get the liner out so it would not interfere with future root growth. I am planning on a shrub and perennial bed over the entire area.

I live near the water, so all my soil is very sandy. I have noticed that the pond area soil stays moist longer. I know there is at least one area where the liner is no longer intact, so water can eventually drain out and it does not become a mud pit after a hard rain.

I am beginning to wonder if leaving the liner could help hold moisture, and stop nutrients from just leaching through? Could I just make sure that I have adequately chopped some holes through in any area I may want to plant something that would want deeper roots and let the perennials live in the moister upper strata? Or should I go ahead and dig down the 1-2, or even 3 feet to try and pull that liner out? Thoughts? I appreciate any input.