It's about the constant necessity when building a certain item to have the previous version of it in the recipe, having this happen once is ok, obviously, twice is fine but almost not (as in an MK3 having the MK2 on its recipe), the issue is when items go to higher levels and creating even one requires a massive list of items, sure, later in the game they are all plenty, but nevertheless it takes a lot of unnecessary time to build them, why would a steel steam engine need the iron one to be built, and why would the titanium one need the steel one in turn, admittedly this works very well with intermediary products, circuits as an example, and they in turn are fine as is.
The main problem created by this is that it makes the path to the endgame more linear, and prevents the player from directing his efforts into a specific path, also prevents any focusing on a specific material, the good part of it is that it keeps all minerals relevant through the game, but this feat would be better invested on alloys that could be on the recipe, and of course, circuits already use most of early game minerals.
On modules I'm on the fence about, its a major harassment to build higher level ones but they're not really mandatory for anything so It's way less of a problem.
I would like to hear other people's opinions on this and maybe Bob's version of the story too.
All in all, excelent mod, definitely my favorite compilation on Factorio, keep up the good work
