Lemmygrad is not a large website. The statistics on the sidebar shows that it has around 10.5k users, with this number being considerably smaller in regards to its active users, with 1.11k users using the website in the last 6 months and half than that in the last month, with 591 users.
That is perfectly okay: the concept of a small, tight-knit community of active users with shared interests who can recognize each other frequently by name is an appealing one. However I personally think that on a site with a membership so small one should stop to think, before creating a community centered around certain topic, about the chances that exist for such to attract enough users and grow to the point needed to maintain a certain life. I would have imagined that it should be a matter of common sense, but it seems not everyone gets it, and as a result, Lemmygrad ends up full of extremely niche communities that have either no posts nor users except its creators or recieve content solely from these ones.
We have seven communities dedicated to Australian cities, all of them created by the same user and all of them without one single post. We have a community for clarinetists. We have a community dedicated to The Critic. We have whatever this thing is. Most recently we got a new community for Maltese communists, which with all due respect, as a country with little more than half a million people, it has absolutely zero chance of catching on in the slightest and is going to become either another abandoned community or someone's own personal blog (of which we already have our fair share).
The list goes on and on and all of these are just examples. I am not asking these specific ones to be removed: I am just using them to point out a problem that makes the section of Trending Communities irrelevant and unusable and the List of Communities tab completely unnavigable, amongst others, as well as to make the case that we need new policy in regards to the creation of communities and/or the elimination of those who become either abandoned or populated solely by their creator.
Ok, so what's a sensible way to determine what needs getting rid of? I think we need to start with what the point of engagement here is to begin with and go from there on what is practical for improving it; I cannot offer much to say on that as I'm not very familiar with how it got started and what the goals are beyond certain baseline ideological positions. Your argument seems to be starting with the premise that making the Trending Communities tab more functional is intrinsically an improvement; but to what end, I'm not sure. Personally, I didn't even realize the tab was there for a while. I was just going by the main feed. I have used it a couple of times to find recent communities I'd seen where I had an idea for a post that was topical, but I have not actually used it yet to explore communities.
I cannot offer hard data on what helps with engagement, but I can say that in my personal observations across more than one forum over the years, it appears to be the case that there's something of a tightrope line to walk between restrictions and chaos, and many a forum ends up accidentally chasing people away because it ends up in a process of following the letter of its law and losing sight of what is getting people to show up and talk and stick around. On the other hand, I have also seen at least one forum where it appeared to be a sort of enforced chaos; the people in positions of curation refused to put their time into doing so and so whatever was most popular and loud ran the place, which effectively undermined the point of what it was originally about.
Here I know there is a certain amount of curation that is vital in order to prevent it from being overrun with debate brain liberals and other such types. But in terms of what is useful to the cause within the right ideological lines, I'm not sure. Perhaps if there's someone around with experience in social media engagement, they could be of help here.