The fact that - up until recently at least - it's been very hard to just be a passive attendee in the JWs may well have a large part to play in all this. Until recent significant changes, it's not really been possible to identify as a JW and "associate" without significant effort.
Unlike many other faiths where it is sufficient just to turn up to the local place of worship now and then, the JWs have demanded considerable effort to be considered one of them. Attending two (originally three) meetings a week, monthly report of "significant" field service (usually at least 8-10 hours), regularly meeting with your local group for "hall cleaning", twice yearly circuit overseer visits and assemblies, a Memorial and a summer convention, and so on. Any significant failure in any of those areas used to result in awkward questions at best, and at worst, the dreaded "shepherding visit"!
I'm sure this is a significant part of what has kept the numbers steadier for the JWs compared to many other religions. Until very recently, you've really had to work on being a "member" (and at the same time, suppress or erase any doubts or tendency to relax/back-pedal).
However, I do suspect that the many "simplifications" of the past 5-10 years will begin to significantly eat into the JW numbers soon - perhaps in the next 3-5 years, and growing after that. Having said that, there is the opposite possibility that by becoming "JW Lite", still with the promises of paradise and resurrection, etc, but with a "softer" approach to discipline and lower "barriers" to staying in, that might actually give them a short-term boost, as inactive ones, hesitant family members and others who have previously hovered on the edge of the JWs might decide to join now.
I’m still reeling from the fact that people don’t have a physical Bible and don’t bother looking up the scriptures any more.
I'm with you on that. I've kind of got over not hearing the rustle of pages, but the fact that there are practically no physical publications used at all is so weird: the speakers use tablets, the songs are projected on screens, and everyone follows on their phone or other mobile device. And of course, in several places, significant numbers are not even physically present, but connecting online on a regular basis!