For one, your site has 157,000 topics, yet the busiest discussion only has 64 replies. Looking at that topic the replies aren’t responses, they’re text lifted from websites such as TheSpruce:
Have you considered the possibility that in its current form Google might be right?
When Google indexes a page the contents are compared to other pages already held within the search index. Google knows where content was first posted. When it detects duplicate content which has been copied from other sites, it will treat the duplicated copy as blogspam.
We really can’t give you tips on how to cheat the algorithm, even if we could this behavior is deeply unethical.