My oldest son when small used to built forts and walls with playing cards.
I made aircraft carriers out of shoe boxes and fashioned the jets out of tinfoil. When they bombed an enemy city, I would use torn-up black hefty bags as the smoke.
Give boys time, and they can create worlds out of anything.
Taking Legos from them is just cruel because it tells them that their natural desire to control and change their environment by building and creating is “wrong”. And it hurts the girls that dont even want to play with the blocks.
"Forts win Wars!"