Hi! In general, the main stumbling block was time :-) Initially, it was planned that there will be enemies present and this should already diversify the gameplay enough. Next, the goal generator creates random events depending on the situation: exploration, attack, rescue. For example, completing a scouting task should trigger a mission to destroy enemies (possibly with allies). Then, after completing the attack mission (depending on its results), the player receives a mission to rescue astronauts who were evacuated from the destroyed ships.
This all together proved difficult enough to complete in a reasonable time.
First of all, there were quite a lot of problems with AI — it was difficult to get other spaceships to fly around obstacles when chasing the player, and this also required code processing (my architectural mistake). In this regard, the game is somewhat more difficult than the classic shooter with a top view due to the presence of the surface and mountains, therefore, it already required the development of a full-fledged path finding.
In the second place — the system of dynamic missions, and I just did not have time to build it properly. Another element that I planned to add is ground armored vehicle with weapon.
I am currently thinking about how to really rework the source code of the game and add the missing elements, but it seems to me that this will not be soon and already a separate project (it is unlikely that I will have time to do this before the end of voting).