Thanks for having held these contests. They have been going almost 3 years so I think that is just part of the natural life cycle where it feels like most things have been done in some form or another or people have moved on to do other things. I remember way back in 2015 when there were 15+ entries to the building category.
The idea Jat was talking to me about in December would be interesting to see followed through, the "themed ideas". So for pics, the themes could be like "carnivores" or "action" or "colorful" or "black and white", and similar key words for other stuff, like build a dinosaur for arkitect, create a vehicle, a ship, spaceship, etc. I think having such a specific focus might create more appeal since you won't suddenly have someone come along with a massive village that took 200 hours or something, and levels the playing field a bit more.