While I can see how LEGO sets have indeed become less imaginative in the box (all these sets that are specific for one use) unlike the creativity that was required when I was a child playing with LEGOs, that does not change the fact that you can use all the pieces in creative ways. Instead of embargoing LEGOs, maybe you should use them to teach your children to be creative in coming up with new ideas. (This is not meant as a commentary at your parenting skills - while typing this I can already see it as potentially coming across like that since I can't convey the proper emotion with text on a screen - just offering it as an alternate viewpoint).

LEGOs gave me the power to use my imagination and creativity to build what I wanted, and this empowered me as a child, and honestly I believe that it also gave me the analytical mindset that has translated over to my programming career.