The pipeline bottlenecks all changed in favor of bruteforcing the things that BSP had been solving with an elegant precomputed data structure - what BSP was extremely good at was eliminating overdraw and getting to where the scene could render exactly the number of pixels that were needed and no more. It's optimized around small, low-detail scenes that carefully manage occlusion.
More memory, bandwidth and cache means that more of your solutions are per-pixel instead of per-vertex and you can tolerate overdraw if it means you get to have higher polycount models. Likewise, the environment collision that was leveraged by the BSP process reduced the number of tests against walls, but introduced edge cases and hindered general-purpose physics features. Scaling physics leads in the direction of keeping the detailed collision tests at their original, per-poly detail, but doing things with sorting or tree structures to get a broadphase that filters the majority of tests against AABB or sphere bounds.
On a Wii(original Wii) 3D action game I helped ship, we just rendered the whole level at once, using only the most basic frustum culling technique; the hardware did the lifting, mostly through the z-buffer.