The comparison with Rust is not quite applicable since Rust is a pvp game. All pvp games have the advantage that you just need a working scenery and the players do the rest of the entertainment, the developer's only taskafter initial development is to balance everything.Rust, a game that is horrible, has 5x the people playing it at the moment.
Any single-player and even cooperative game has a limited life time (counted from release of the first playable version!), any amusement must come from stuff/stories/NPCs planted into the game at a speed that is much lower than the familiarization speed of the player. I bet you anything that maximal 2 days after TFP release the complete story module for Navezgane the first player will post "Killed the Duke, reached the end of the main story, what else is there to do?" in this forum.
Actually the early access development model best fits pvp games as only their lifetime is long enough to encompass the ea phase and a final version phase.
If you are speaking as a pvp player, well, lots of other fish aka games in that pool, I'm happy that this game caters to single/coop players first.
If you bring something like skyrim as a counter example to the limited lifetime of SP-games, all the bethesda games have a declining user base comapred to release, and that would be even more pronounced if they didn't have modders to add content all the time.