I think it's waiting for some new event that will drive a lot of people away from Reddit again to achieve critical mass and finally outgrow Reddit.
In the meantime, I'm trying to keep my little corner of Lemmy alive - my dinky little special-interest communities - so that those who don't want to partake in the big Reddit equivalents know they have alternatives on here that are not stale.
Reddit, like Facebook, has the advantage of inertia: most people are on Reddit, so other people patronize Reddit, making Reddit even larger. And just like Facebook, it takes something particularly egregious from Reddit to get enough people to walk out at the same time. And you're correct: Reddit has learned to slow-boil the frogs to avoid this.
But - maybe I'm naive - I'm banking of the Fediverse offering consistently better quality and less drama than Reddit to slowly attract people who want something better, and I'm trying to do my part to increase the S/N ratio on here.