Hey, just started playing the game and my first impression is that it is quite slow at the beginning. There is no door at the start so there is a short period of confusion which made me wonder if the game is broken. Then once the doors start spawning the time between spawns feels too long. This made me go here into the comments to leave my first impression with you.
The feeling of slowness seems to stem (atleast I personally found so) from the workers having this odd cooldown between opening doors. IMHO they should just dash from door to door whenever one is available instead of standing around for several seconds in between. Otherwise the speed upgrade just kinda feels like "meh".
Otherwise I like the concept of an incremental game about doors! Very interesting.