When I was a kid I used to spend entire days building and creating new stuff once I built the designs from the booklets. Today when I see a Lego kit is kind of another toy: is designed to build one and only one design, compared to the generic kits that were sold and also popular many years ago. All these new kits pieces are just to accomplish one build. The Lego spirit of ever combining and creating with same pieces…
There's a lot of re-usable parts even in new LEGO sets along with the custom pieces designed for the model. I just built the new LEGO Road Bike (https://www.lego.com/en-gb/product/road-bike-11380) and obviously it has a bunch of new part numbers for the wheels (it's the biggest tyre they've produced and they are the biggest tyre manufacturer in the world). Other than the wheels, there's some clever re-use of custom parts from other sets such as in the handlebar or brake calipers. I was impressed by how they've put together a build with things at strange angles and hardly any exposed studs.