My kids have a mix of classic & branded sets and the play area is a mix of designed builds and improvised creations. The favourite and larger sets stay in their own bags when deconstructed but most others are added to the common boxes, which are sorted by rough shape based on what we’ve seen stimulates free building. There are a lot of complex shapes but many of those are useful in free building. I’ve purposely bought some sets with multiple complex flats & bricks as they allow more creativity than just the basic bricks.
But I know other children who just like to follow build instructions or just like to play with the characters and that’s OK. That’s the flexibility of modern Lego.