Thank you for the excellent feedback! I also noticed that during my own playtesting, but to be honest, it was partially a benefit for this jam. I had no time to optimize the game, and i found that keeping all the machines for every word makes it start to lag pretty bad XD
In the future though, you raise an excellent point. It would be nice if the player had a reason to keep around the old factories, and games like Factorio and Shapez.io offer some ideas of how to offer those incentives. I'll keep at it! Cheers!