That statement the game is going to die when finished is plain stupid...more and more people jumping in as it gets smoother less buggy and gets more features. I know quite a few guys who doesn't like half baked games but said when it's ready they will buy it because they like what they saw so far.
Your other statement is completely just guessing..if Egosoft or Frontier had to write the engine from scratch and build up the company on the fly they'd probably in similar situation. Before you argue about Frontier..they were an established company way before Elite kickstarter and the Cobra Engine was worked on for years and years before their kickstarter.
Why do you think they didn't release space legs? Because their engine is not set up for it, and to get FPs in it takes long long years.
Building an FPS universe is several magnitudes bigger work than a "you are the ship" game. human and alien characters models, animations, character generator, clothes, weapons. usables, armor, doors, lifts, spaceship interiors built to make sense and match the exterior..same for stations. All teh textures set up to be looked up from few centimeters instead of hundred meters like in elite, the list is endless. Now that SC has these, Elite either releases a half assed space leg update and get crapped on compared to SC or they try to make it comparable to SC which needs basically an engine rework and 80% of the game reworked which takes years.