I definitely don't disagree. Endgame is what defines the lasting power of a game, anyway. But, if the climb to endgame is extremely challenging, it doesn't serve the endgame focus any better. I don't agree with the idea of nerfing, but I acknowledge that nerfing is sometimes necessary for balance. However, if a system is that off kilter that the first step is a nerf, that leads me to believe the design was inherently flawed. In this case, the workshops need to be adjusted to make them more profitable so that the only option isn't a bunch of tanneries everywhere.
Can players influence this some? Sure. Keep routes between your cities clear of trouble, and hell, pick up a supply of raw materials on your way as you learn which cities and introduce those materials into your production cities. But that is an aid, not a fix.
My whole point is that yes, balance of some form is needed to ensure that the trade system is made functional and frankly useful. Nerfing Tanneries since they are the prime end-all right now seems far less useful than addressing the trade system as a whole and making sure other workshops can keep up, given the supply and situation. The point is moot, however, as the game is still Early Access and they have a plethora of other issues to track down before proper balancing can begin.