It's about creating and keeping things moving rather than just consuming. I wouldn't expect lemmy to move as fast as reddit because the focus isn't in having an algorithm or creating a selection of communities to prop up the front page. It depends a lot more on the user's curiosity to find an interesting space to comment or share links or media. Removing the commercial aspect of it, removes a big drive for engagement by design.
Lemmy being free of modern engagement tools will always make it a slower, less interesting site than reddit or any other social website. It could have a similar fate to older web forums if we expect it to perform just like commercial social networks, we should be conscious of that and refrain from proprietary networks and visit lemmy or other fediverse alternatives when it's interesting to us.
The reality of most of this websites is that they aren't really necessary in our lives, the reason they're kept alive is because they're designed to make us keep an eye on them and fill us with not actually necessary content. We aren't users, we are used by corporations so they can put an ad in between, or to gather information about us, so that their customers (those who pay for ad space) can pay for their service making the best targeted ad campaigns possible.
I'm not sure if you are really active on lemmy's ML communities, but there's plenty in lemmy.ml. I don't participate in them, but I do try to keep posting in the instance I like, you're welcome to post and comment wherever you like. :)
I honestly do want it to become bigger. We need to share and produce more and constantly, otherwise it will wither. I'm interested in your opinion though, if you're willing to share your discrepancies, I'll read it.
Also, yeah. Since lemmy.ml and the main developers are marxists, ML can be understood as marxist-leninist. Big lefty influence on many instances. Honest question though: Have you tried posting ML links or opening discussion threads on it?