Just to put the other side here, we had a similar philosophy when our DD arrived in the summer last year, and didn't buy any toys other than a couple of soft toys to decorate her room. But relatives and friends bought a lot of stuff that we were very cynical about.
We were surprised to find how much she interacted with it all. My brother bought a 'jungle mat' which we liked to lay her on even when she was days old - I have a video of her aged 7 days, reaching out for the hanging elements of this thing, which is apparently unusual (I wouldn't know, she's number 1!).
We've made a lot of 'toys' such as jars containing rice, letting her play with pots and pans, straws, 'found' objects such as pine cones, leaves, a wooden spoon and so on. We felt it was important that her experience was broader than just plastic!
Aged 10 months she started doing that thing where they hold a toy and 'walk' it along a surface, babbling to it. Seemed quite advanced to us, and so we've encouraged and permitted it.
And so far we've never had that problem where she prefers the cardboard box to the toy. If we had then we might have stopped buying toys.
I look at our living room with two big boxes full of toys and wonder if we've done the right thing. But then when she comes down in the morning and I can see such imaginative play, it feels right. She loves books, dolls, vehicles, animals, crayons, Play Dough - it feels right.
Also, my mum has a box of toys at her house, and DD very quickly runs over to it when we arrive, pulling out a fresh set of books and toys.
We joined a toy library and its brilliant - a couple of quid for the year and we can borrow what we like. It's a great way to save money.