The Assembly shown in these two videos stitched side by side:
Resulted from STEP file:
14,104,909 Graphics-triangles
18,975 Surface Bodies
1,224 Solid Bodies
33,689 face-level appearances
The difference in speed is due to how SW 2023 computes appearances (SPR 1127113). If you work with components containing complex imported geometry, SOLIDWORKS 2023 will open you files several times faster than older versions. The same goes for drawings containing these files.