The whole game is stunning quality for what is still "alpha", where in games that frequently denotes "so buggy it's a miracle if the game runs for 10 minutes without crashing and burning".
It just works, and it's smooth as silk. It seems like they've concentrated heavily on the game engine and now are focussing on content, but there is plenty of content already to play with.
The trick is to realise that thanks to the rise of "early access" in indie games, "alpha" means release, but released absolved of any sort of commitment to continue to develop the game or ship quality software. Final "release" versions are often really "end of life" _final_ versions with no future expansion.
It's not to say that many indie (and not-indie) devs produce good games under this model, it's just there's been a huge shift in what players and developers expect from each other, as well as how they market it.
Similar parallels can also be drawn to the pre-paid kickstarter systems which were originally intended to help pay for upfront costs like manufacturing, but are now really used as risk-management tools to help ensure a certain number of sales before a project starts in earnest. There's no reason Peter Molyneux should need to ask players to pre-fund a game [1] of unknown quality and even scope, for example.
Well factorio is actually following the minecraft design. They have a bunch of things they want to add, but due to the complexity of the game it takes time to get there. Like in minecraft where they kept adding blocks until they were like "alright we have all of the ones we initially designed in". Factorio hasn't reached that point yet.
It just works, and it's smooth as silk. It seems like they've concentrated heavily on the game engine and now are focussing on content, but there is plenty of content already to play with.