I actually think we're doing fairly well, all considering. Back in 2014, we were a lot quieter. Wikias never really get hundreds upon hundreds of people on board. But those who do eventually find their niche. We're still about where we should be given our age and being a wiki based on a living franchise, not a dead one.
While not still as popular as likes of One Piece wikia... They've been around since 2004, we only kicked off in late 2010, to the point I'd say we're about 7 years old. And even then, for a wiki that's been around for half the number of years they have, we're doing better in my opinion then them. But the biggest issue they faced, which we didn't, was they were an early 2000s wiki and it took time for people to get on board with wikis then. We'll likely be more on par with them when we're as old as 14, if Vocaloid continues as a franchise that long.
The only downside is we don't have people who visit every week since we're not based on a serialised series. And most never venture too deep into the wikia, whereas with the OP wiki you may have to re-read who certain characters are. Or reading on certain chapters again. We just have people perhaps visiting the same 100 pages as a result constantly.
Edit:
Like with VO forums, a wiki as with a forum attracts a particular crowd of nerds and geeks. Despite Azure claims VO forum was still doing well for a forum. Likewise, we're where we need to be for a wiki. Honestly, just visit some other wikis, aside from Wikipedia most don't get thousands of visistors a day. I've been in discussing about this wherein people have to be reminded their the "vocal minority" and only represent the small % of fans who discuss, the rest being the "silent majority". So most fans aren't making their presence known. If you want to compare this with something similar, check out a popular youtube like Mattias, Markiplier, etc. Now each video gets hundreds of thosuands of views, even past 1 million or above. But comments may struggle to exceed a 1,000, while thumbs up for the video get about 100,000 ups if likely. Sure millions of people may view the videos, but once the video is over, they'll skip leaving comments, thumbs up'ing the video etc. In fact... ITs more often then not viewers don't even watch the full video. :-/
So you'll never get every vocaloid fan involved with the fandom and we're lucky we get what we get.