The TL;DR: Analysis showed that most frame time was lost due to lack of LOD levels and culling - causing the engine to render insanely high amounts of polygons

The TL;DR: Analysis showed that most frame time was lost due to lack of LOD levels and culling - causing the engine to render insanely high amounts of polygons that weren't even visible on screen. In conclusion it seems that using the brand new engine feature DOTS (which is a perfect match for this game), successfully solved the CPU bottlenecks the first game had. But because of Unity's DOTS <-> HDPR integration still being WIP (with several key features being experimental/missing) - they had to implement a lot of stuff on their own (including, but not limited to culling), which cost development time and caused the game to be not quite ready at release (explains missing LODs/optimization).