The issue that will kill the game.
While there are many issue that need to be addressed or ironed out from the general lack of progression goals, limitations of the cubic nature of the structures, pacing in terms of how a player goes about clearing an outpost, movement clunkiness, and the game being balanced in a way that promotes spam over creativity, I don't believe that any of these issues are in as urgent of a need to be fixed as the outpost pathing system and requirement.
In the current version of the game, the player needs a walkable path that allows for this box man thing to path find to the final objective. The path can not go up or down vertically, it can not be broken in anyway, and the player is not required to beat there own level to publish it or make it active. By forcing a player to have a perfect walkable path, the player is forced into designing their outpost in a certain way eliminating a large amount of variation in design that would be possible under a more open ending pathing system. Players could make maps that require some amount of parkour or engagement more more complex movement which could give the game much needed variety. One of the systems used in similarly designed games like mario maker is the requirement that a player must be able to beat their own level. Making this a requirement before publishing a level could be potential fix the part of the pathing issue so every level is beatable.
A game like Meet Your Maker's success is highly dependent on user creativity and how the game respects it. In its current form, the pathing requirement is the greatest limitation to player creativity and expression and needs to be reworked before release.