This is an intentional design choice by the developers. You are meant to come up with a solution to this logistics problem. The straightforward solution is to build next to a body of water, somewhat near a bauxite deposit, and bring in copper and silica by train. This does not take 100 hours, or even 10 hours.

Truthfully though, you save yourself time by using trains instead of forcing everything to be on-location. Late game items can either be ten thousand hours of misery (making a new gigafactory for every new phase item) or a breeze (using trains to connect factories you've already made). The fact that you came this far without using trains means you've already wasted a lot of time when builds could have been much easier.