Lack of further content to discuss. Unlike Niki, Anon deliver his updates in big batches, though that does mean he'll take longer to deliver. Plus, he's currently reworking the game to run on another engine (I forgot what it's called) and not ChoiceScript since he got booted by CoG. That adds to the load. It'll become active again once the update is out (projected to be before Halloween). And then will promptly die again a few weeks after that.
Less frequent updates means less engagement, but higher peaks (as in the peak of the 'mountain' of a graph, not the quality of the story LMAO) when update does drop.
Anon also doesn't add content to previously done chapters (like Niki adding the cousin visits) or change previously established lore (like how the Tang Wei talk, which have already changed before, now have changed again as per the latest sneak peek where he tells you the two method of cultivation), so less reason to replay the game once you've finished your desired playthrough.
We also don't have a love-hate relationship with the MC or author like we do here. Practically everyone agrees that the MC is actually great (written well and treated well) and that Anon has a good grasp on his story and direction. Unlike Niki where it changed from 'Cultivating from Houtian to Shangtian' (original version) to 'Cultivating from Qi Refining to Nascent Soul to escape from this world and explore the proper worlds' to 'Actually, you don't have to do that since you're getting invaded and the PoMA world will be merged with a proper world LMAO'.
Addendum:
The lack of leaks also hurt the engagement. We have constant drip of in-game and off-game content here (like character Q&A, side stories, etc.), but we don't seems to have that for AC. Hell, people keep asking for the AC side stories in the WIP and Leaks thread but never seems to get answered.