I think the main thing here is that forums are driven mostly by the people who post day to day. And the loudest most active crowd are those simply promoting.
Years ago, it was still very much a creator's space, but most of those creators made threads talking shop or discussing the creative process. Some of these threads pop up every so often now, but don't get nearly as many responses as the old days as the bulk of users on this forum are just here to promote and not deeply interact with a creator community. More seasoned creators have gone into closed discord servers or elsewhere to get their creator community.
Readers have never had much of a presence on the forums for as long as I've been on Tapas (since late 2015 before I was even a mod). You'll get readers occasionally posting threads asking for help finding a series, a couple of threads gushing over a series they like, however those threads never get many responses.
Even with the current Tapas Discord, it is very much a creator's space. I've seen a few readers go on there to ask when some premium series will be updated or ask where the free series are in general, but that's pretty much it.
I'm sure there are some readers who do lurk the forum and discord, but they are very much less prone to posting and making their presence known.
In the past Tapas has directed readers to the forum during reading events on the main site. However, those users will just post in the dedicated event thread and not stick around to check out other threads.
Even in a reader space like a series itself, new creators are always asking how to get interaction with the followers they do have or get comments under the episode. (Usually the answer is to prompt a question in the episode description.) So I think overall, most readers will be very quiet. If they have a presence online, they will most likely talk to other readers in places like reddit or post on social media to share reviews, fan theories etc, places where there are other topics of interest to them other than strictly webcomics/novels.
I agree that the forum is not what it used to be, but really I don't know if there are many practical solutions that can realistically change its landscape without a serious effort from the userbase. And I'm not banking on readers to flock here even if there is an overhaul.