I think that short Metroidvanias are interesting because it can be a game design challenge to make the elements that are core to the genre work within a small time constraint. Sector 781 is certainly short, clocking at just about a half an hour, but it doesn't do anything to help itself stand out. The map and powerups are nice, but traversal can be annoying due to how rapidly your jump height decreases. The boss fights are also plainly repetitive, simply doing the same back and forth pattern while spitting out identical bullets. Not the worst way to burn a half hour, but nothing standout.