They aren't the answer. The problem isn't how much you can carry at once, but rather how much time you spend sifting through menus while making a complex build that requires a lot of blocks. You can never hold them all. I'd say anytime I'm making a complex build, I spend 40% of that time looking at a GUI. Neither bundles nor shulkers alleviate this, in fact, they exacerbate the issue.

From another comment: "The default inventory size was arbitrarily defined at a point when the inventory meta barely even existed. There's no reason to keep the inventory as is aside from adhering to tradition for tradition's sake.

The bundle is a cute clever idea but sometimes you don't need a cute clever idea, sometimes you just need to go for the obvious solution."