There is value in some toys. Lego, especially, is very good for brain development if kids are actually building and not just playing with "playsets". I'm also quite keen on old-fashioned wooden toys. DS's train set and tractor are wooden, not plastic. They'll probably still be around for his grandchildren!
However, kids really do need to use their imagination, and many mass-produced plastic toys do not allow for that. My DS loves to garden, but in his imagination the garden is peopled with every kind of fantasy creature you can imagine, as well as all his favourite story book characters. One day he's making a toadstool house for Big Ears, and the next he's making a tree house for the Berenstain Bears. And yes, he sees fairies at the bottom of the garden!