You don't put a ton of work into end/late game until the basics are practically set in stone. That is game development, or at least good game development. It would be a huge waste of money and resources to completely flesh out late game and then change the underlying structures. According to what type of changes you put into something like AI or physics it is possible you would end up having to scrap almost your entire end game and start over.
I see this type of comment on here all the time and they all boil down to this, "We don't have a complete game yet. Where is xyz?" Welcome to EARLY access, early as in NOT complete. If you have a complete game, it wouldn't be called Alpha. It would be Beta or even Gold.
If you sign up for Early Access, you should expect that the further in the game you play the more things you will find missing or incomplete.