Duplo is interesting, it allows kids to quickly build pretty massive stuff if they have enough of it. But mine were done with it relatively fast and we ended up donating it to other people.
We have a large box of duplos but my three-year-old isn't interested at all, maybe showed some interest a while ago, but mostly to build the tallest tower. Now it's time for the real legos, but I'm not sure if we'll even get any if she won't play with them.
My 2 year old daughter hasn’t really shown any interest either.
It’s weird, as a kid I wasn’t really into building stuff. Lego, wood blocks, etc. The only exception was “forts” in my woods. I could play with my Power Rangers toys for hours.