At the end of the day, even if it's home-made, the engine is just a tool. It's making a damn good game that will make money because it's marketable to the general public across the world - a much larger market.
Yes, the I-Novae engine has a huge amount of potential, but the company is still small, unknown and kind of mistrusted. They need the money from a successful game to catapult them into making bigger and better projects.
This in itself is a challenge in such a crowded market, so I agree that engine features should not be priority right now. The combination of features it already has are pretty groundbreaking.
So, as said previously, gameplay, gameplay, gameplay! (For now...)
I'm still waiting for the full MMO that will point at Elite's limitations and laugh hysterically. But I:B will keep me occupied in the meantime!