Are there in Fallout 4 weapons that have to be crafted??

No, not really. The crafting system is all about modifying weapons that you find - there aren't any (aside from grenades) that you can build from scratch. Kind-of a pity, really - finding those rare blueprints was a nice aspect of Fallout 3.

yes, true.

I'm hoping a mod can allow craftable items to enter fallout 4, I do find weapon crafting to be just as, if not even a little more desirable than simply finding legendary enemies and looting legendary items.

I wonder why Bethesda deleted crafting.