Smaller textures, more assets, and worse audio mainly. Textures used to be like 512 for hero props. Now even random objects you see a few times get a texture 16 times larger. And they get up to 4 of those for each object/group of objects. Thanks to pbr and normals and whatever other masks and lightmaps may be required.

Im sure there are more reasons for size bloat but this is from us artists at least.