You could certainly build things that were possible before, but I'd rather suggest entrepreneurs go towards that, which wasn't. And if you do build something that was possible before, ie- Dropbox, then I suggest you use the building blocks to build an iteration that wasn't possible before. Dropbox was started as a small project by Drew and eventually a YC funded company with a small 25k in capital. It wouldn't have been possible to do Dropbox before AWS,etc. without spending a ton of up front Capex in hardware you may or may not use down the road.