(Late reply, but whatever.)
This is kind of why I never really used BookWyrm. I tried it out, realised I have to add like half of the books I’ve ever read (and many that I have read have shoddy or incomplete metadata), and left. Now I stick to writing down everything into an excel (actually LibreOffice) table. Any fields that I need, I can add at any point. Now, it is a bit more complicated to set up at first (deciding what data is relevant to you, entering it all into the table), but in the long run I find it a much better option than any online service.
True. It takes this sort of effort to build a good database with users’ input, and plenty of patience. And Bookwyrm does seem to deserve that effort, unlike… some of the competition.