Simplifying the shapes to a single coarser resolution is a quick fix. Beyond that, rather than doing it ourselves we should look into an existing "vector tile" solution. There are many plugins for Leaflet that render vector tiles, none wrapped for dash-leaflet as far as I can see. I'm not sure how we would generate the vector tiles on the backend, but I'm sure someone has done it before.
Simplifying the shapes to a single coarser resolution is a quick fix. Beyond that, rather than doing it ourselves we should look into an existing "vector tile" solution. There are many plugins for Leaflet that render vector tiles, none wrapped for dash-leaflet as far as I can see. I'm not sure how we would generate the vector tiles on the backend, but I'm sure someone has done it before.