I'm really not a big fan of Early Access (EA) from a consumer perspective, but as a emerging developer you'd have to be crazy not to try and exploit it.
Even your good EA examples I'm not so sure of. I mean KSP seemed to be permanently in EA, I suppose it has released by now. And I understand darkest dungeon had a controversial EA development, with some people still not liking the changes.
The only EA game I really rate is Squad; the game is already really fun and they do the probably best dev posts I've seen
https://joinsquad.com/#updates. They are also making a commercial multiplayer game from a multiplayer mod, so its early days squad still could somehow fail, but I do think EA can be done right.
You just need to have the basic gameplay polished and then expand the content, but this is probably easier with a FPS than less trod territory that OKAM is treading. Squad is essentially the same gameplay from an already successful mod (PR for bf2) in a new engine. I assume OKAM is very different to crpg/strategus.