There is a suggestion the current GB might be about to change the 144,000 teaching in some significant way.
If true, this would be just yet another in a string of major doctrinal changes, which of course follow on from their (relatively) recent and now (in)famous admission that: "The Governing Body ... can err in doctrinal matters or in organizational direction."
In the face of all these fundamental changes, it's no wonder that most of the current R&F are losing their "zeal" (to use a theocratic word). Of course, other churches change or reinterpret their beliefs too over time, but there can't be many that are as 'extreme' in this way as the JWs.
For example, once changed, you will never hear an "old" Kingdom song or have a previously respected WT publication referred to again. Their entire history becomes expendable. It's hard for many people to maintain their enthusiasm and vigour in the face of the wholesale disposal of what they were once taught to hold dear, especially when those changes start to become commonplace.
Before the mid-1990s, change in the Org was glacial (at least since the 1975 upheaval - that's before my time with the JWs). But since the early 2000s, there have been numerous major changes, and the pace has increased even more since about 2014.
So it's no wonder that spark is missing from most of the R&F today. The 'oldies' have lost it due to disappointment and being tired waiting for the end, while most of the 'newbies' (those baptised since the turn of the century) never had it in the first place, since the religion has become a lot more shallow in the time they've joined.