For a 3 programmer team development is extremely fluid. Some early access games are lucky to even get 1 update a year.
Development is an on going process and features are being added to the game that the community has requested, larger features like cavalry obviously take time, AGS has already stated that it is coming, and trust me when I say it is indeed coming.
As for other games of a similar genre I personally don't believe they pose any threat to the future success of Holdfast and I'm sure they will have their own development delays and troubles of their own. It's all well and good complaining about development time but until you actually experience game development yourself you don't understand the time and effort that is required to create a game. I think people need to be a little more understanding, I know it can be frustrating to wait but people knew what they were buying into when they bought a early access game.