OK, this is an easy fix.
With all the old classic shes, that part of the feet that stick through were hidden by invisi-prims. This was a work around built in temporarily until they got alpha layers for your system body. Those old invisi-prims have not worked in a few years. Now, we wear what is called an alpha layer like it is a piece of clothing. What this does is turn your body transparent where the texture is.
What you need are some generic shoe alphas. Below is a link to a free set.
Wear the ones that hide what you need, most likely just the very bottoms of your feet but some of the old shoes with prim toes and feet will need you to hide more.
Anyway, play with these for now and welcome back to SL.