Well... the thing is building an audience is, for most people, a marathon, not a sprint. So yeah, maybe you should have been a bit more careful rationing out your updates, but you know, these things happen. The thing with the forums though is you also need to ration out posts in promo threads here too. Sometimes I see somebody come onto the forums and post in every single available promo thread in one afternoon, and then they're gone, and it's not very effective. It's better to do one or two a day, and also to be in other threads, like ones about art and writing, or where people seek critique or advice and to just try to be around. A lot of people won't click on something the first time they see it, or they actively avoid or even mute out promo threads, so you really have to be part of the community to get the most out of the forums.
All that said, you do need to manage expectations when what you're making is a science fiction novel with a cover in the style heavily influenced by retro manga from before a lot of Tapas users were born. It's not that you can't build an audience with unusual works like that on Tapas, it's just that it tends to be slower, but balanced by more engaged and passionate readers, because you're making a niche work. You will have to work hard to find readers and really search for them all over the place, because what you're making is so different from what's familiar on the platform (Romance-centric works, often Fantasy, in a more modern Korean-influenced style).