I have a 5 yo that is very enthusiastic about Legos. It turns out that both directed and free play are good.
He gets new kits and starts by following the instructions. He learns techniques along the way. How to interlock to make things that are strong and won’t fall apart. Patterns for building subassemblies like body panels or spoilers.
As soon as he’s done following the instructions he takes the whole thing apart, and starts building his own creation with the pieces, applying the concepts he learned.
It’s kind of like music. You don’t learn to play piano by composing songs, you start by playing other people’s music to learn the fundamentals. Then you can start riffing on it.