First of all, the game hasn't been in development for 6 years. The demo created for the kickstarter video was just that; a demo thrown together. It was very basic. It didn't contain the thruster-based propulsion system we have today, nor the ship damage models, nor the ability to change out modules, nor the ability to walk around ships, nor persistence, no ability to go to planets... no nothing. It was literally just the player moving a Hornet through a 3D space with a few asteroids and a Bengal.
Development didn't begin immediately when the kickstarter finished; CR had to spend years first getting the experts, land, and materials he needed, then sitting down with the team to plan out the order in which things need to be done and how will do it, and THEN development began. From the ground up. And then stretch goals were continually added, until CR realized he had to stop because then the game would never be finished. Furthermore, progress has been hampered several times, with CIG needing to pause work on the game to move and adjust their work to a brand new engine. Star Citizen as it is now is actually very near to being what was promised in the original kickstarter promise, so you could say that it's almost finished. CR is still going to press onward and implement the features he promised in the stretch goals. Furthermore, they had to completely remake their Star Marine (first person module) assets from scratch because the company they outsourced those assets made them in the wrong scale, and so on.
They've had a roadmap detailing the plan and what will be worked on next.