>I remember 20-30 years ago when you’d just get a bucket containing an assortment of pieces and if you were inclined to build a house then you’d have to get creative with the pieces that you had.

You are remembering wrong. The kits about building specific models existed back then, and the kits that are just a bucket of blocks are still sold today.

Lego has been selling specific "build a house" sets for like 50 years.

Whether you only build models and display them or tear everything down and make what you want has always been a choice, and most people do both some amount.

There's even the entire world of designing your own "Models". When I was a kid I would build models that represented real things like planes even though I didn't always have the right parts, but nowadays you can digitally design such a model and bulk order the pieces and instructions yourself!