It's terrible that people have such low expectations of artists, specially the authors of this game. People saying this update is the result of even 1 month of development is insane. Remember the devs are getting paid 4k/month on patreon alone. I'm guessing that could mean about i dont know... 20 working hours a week on it, if you are talented and proficient in your world building or whatever you want to call it then dont work /hour and for for content (goals per month), but the standart people should have is not a new enemy every 2-4 months. The challenge in through updates is about thinking new things to add that fit and are interesting, not actually putting them in the game. That could be helped or solved with feedback or patreon updates (that apparently didn't happen).
The people are good at their job or the game wouldn't really matter to as many people, but if you take more than a month to add an enemy i would expect you had to think about ways to involve more things, like new areas, lore behind areas and future enemies (so they make sense in context), introduce some different design for bosses or mechanics, etc.
The update that brought the secret room in the "Playhouse" was worth 2 or 3 months if you also say you are planing to expand on that area, because that's work we don't see but happens; for example.
If there's any other reason, medical, emotional, personal, etc; i think they should come forward and say there were issues and be as transparent as they are comfortable being, with the people that are paying and supporting them.