- move your character - mine stuff - craft buildings - place buildings
And a small bit of combat for the aliens.
I insist, the gameplay IS simple, the content allows for very complex designs.
Similar to programming languages, Assembly IS simple.
Have you played the game? That is, maybe, the first hour of a game that lasts many many dozens even hundreds of hours. Mining only happens in the first five or ten minutes. There are a host of other interactions, from tweaking object settings, optimizing pathing layouts, planning, direction of bots, to deployment of the factorio equivalent of Redstone circuitry.
And mods. As with KSP or minecraft, a greater number of possible interactions comes from the modding community rather than the stock game.
craft/place buildings implies a very discrete action and does not encapsulate the sum of the parts, the interaction between all these systems.
Simple building blocks don't mean simple programs. Heavily interacting components leads to complexity and significant bugs. That's just software engineering 101.
"Simple gameplay" does not mean that the experience of playing the game is simple. Chess has very simple gameplay (basically just: learning how 6 different piece types move, pieces capture each other, and protect the King) but the emergent complexity from those simple rules is truly impressive.
Compare this to say Monopoly, which has a lot more rules than chess, but is mind-numbingly not complex in terms of strategy and the overall play experience.
That is what linkdd is trying to say.
As to your assertion about the game play of Factorio, it is not mine, craft, and place like in a normal RTS. In order to succeed at the game you must design which is a far cry from base building in StarCraft II, for example. Blueprints are indicative of this design requirement.
There are games where you design ships and save templates for them. But playing Factorio all the way through is a much more complicated experience than movement and crafting. Unless your assertion is that complexity of gameplay is measured by input mechanics, which I think is demonstrably incorrect.
That is of course not to say that the developer is worse for it, far from it: a developer that can create a complex game based on simple rules is a better developer imo. But that doesn't mean the rules (and therefore programming them) aren't simple.
Still, the scale of the mechanics leads to more complexity than your average crafting game. If your interpretation of what linkdd wrote is correct, his point is directly controverted when considering that threading discussion in the article. If you know the history of Factorio, then you also know there are many underlying, interlinked systems like that in the simulation that are complex. The software must handle all the ways in which those subsystems could possible interact.
The comparison to Dwarf Fortress is apt. Another similarly complex game that comes to mind is Distant Worlds: Universe, a 4X game that, with all the managers turned on, plays itself.
Keeping that alone bug free is quite the achievement.
I don't think most games struggle because their UI is complex, or because user behavior is complex (there's really only so many things a player can do, especially general ones -- most variety of interactions are "scenes", entirely captured within themselves). At least, most AAA bugginess isn't usually found in their UI. And graphics aren't the complexity generally -- they're just visual artifacts of the engine itself failing.
It isn't. There is significant depth to menus and displays. The way that players can interact with information is very complex, more complex than something as simple as FPS or flight simulator. If we wanted to get very simplistic, Factrio has a much wider variety of button presses than most every FPS.