I think it's also due to the lack of any interest in the current shows.
No one really bothers to make any ep discussion thread for Drive or ToQ, and even when someone does, there's not much going on in them.
When Gaim was on the air, this place was pretty active, even if most of the activity came from Gaim related threads.
Hopefully Ninninger revives some kind of interest and make this place a bit more active.
I do think that relates, but you have to remember the forum was slowing down even when the last couple of GARO shows were airing. And as I recall, GARO shows always has high interest from most members of this forum (even when it does air some mediocre seasons).
But another thing we need to keep in mind too, the online toku fandom has evolved very rapidly within the last 5-7 years or so.
Remember that about 6-7 years ago, HJU and Japan Hero were basically one of the only "non-Power Rangers centric" tokusatsu communities on the internet (Rangerboard doesn't count, as I specified in my quotation marks). When Japan Hero started to lose its steam, HJU started gaining steam due to the toku fandom still being very small in comparison to the other online otaku fandoms.
Flash-forward to about a 2-3 of years ago, sites such TokuNation started being created as the alternative to HJU. Of course, we also had the rise of "groups" in Facebook which basically served as another alternate medium for online fandoms to interact with one another.
So once you combine the fact that CORE MEMBERS HAVE BECOME BUSY WITH THEIR REAL LIVES and the fact that there are now alternate ways for members of the Toku online community to interact with one another outside of the HJU forums, it has basically culminated to where we are today.
In summary, the toku fandom has just grown too much for even HJU to keep up with now.
HJU is no longer the "go-to place" for the Toku fandom to interact with each other as it was years ago