I think the main reason of the drop in readership is firstly kernel development is very involved and detailed, LWN mostly reflects the kernel mailing list and associated events and tech talks.
I guess what I find most difficult as an outsider of the kernel community, is trying to keep up. Jonathan Corbet is doing and extraordinary job summarizing the activities of the kernel community in LWN. But the kernel doesn't maintain any main "Epics" that we have in software traditional development, so take for example fair scheduling. AFAIK, the kernel community does not decide to tackle fair scheduling on the next release of kernel, ie 4.7. Then say power management in 4.8 etc...
LWN ends up with a smattering of various articles under common themes like "Kernel", "Security" etc...
LWN has in the past explained long running topics like scheduling when key updates are happening and I commend them for that.
None of the above is a negative reflection on the kernel community or LWN in how they operate but it feels kinda hard to keep up and stay vested.
Anyways just a few thoughts, will renew membership now.