I was just playing Devil's Advocate! I also understand the reasons of reduced engagement, but maybe a different approach might stimulate more entries.
My gut feeling is that I wouldn't be too interested in very generic competitions, especially as the forum conversation mainly consists of people stating they're sending a bottle in, and then the three winners who might later post a recipe. I also appreciate the issue with Stickies, but that might not be an problem.
I once used a forum for charcuterie and smoking, sadly now defunct as the owner died, but they ran competitions on a bi-monthly basis. The brief was always loose but contained one 'must do' thing. For example, make a sausage that includes and highlights prunes and brandy, or dry cure a piece of offal. There would always be a good lead time so people could discuss the brief.
What then followed would be a very lively (often the most active) thread on the forum as people discussed possibilities, methods, potential recipes, etc.. It didn't need to be a sticky because it was constantly being pushed to the top. The outcome was that people discussed recipes, helped each other with techniques and generally shared ideas. There was no secrecy, so everyone had a good idea of what the others were doing. It didn't matter, because even if a recipe was followed by everyone they'd all be different in some way. The activity in the thread saw more people interested and subsequently entry numbers increased.
Also, relavtive newcomers realised that they could still enter even with very basic products. Many of them would do so not just for the feedback, but also for the support and information they received along the way during the pre-judging period.
What was also very good was that all feedback was published in the thread too. Because people had discussed what they'd done, the feedback was interesting for everyone, even non competitors. It gave people a chance to see how various combinations or techniques had impacted on the final product.
The looseness of the brief meant you never had to make anything you didn't want to eat, but that there was a definitive point that would be judged. However, what was the real driver was that the threads were always active, informative and - because it was a competition of the loosest kind - humorous to boot!
I'm sure the same kind of thing could work for brewing, because the two are quite similar hobbies! I think this post probably explains it a little better than the last one. I wasn't trying to step on anyone's toes.