I have to admit , speaking now as an outsider , that I do remain quite baffled that JWs still have growth , or at least are flatlining. It's possible that another factor is that as the barriers to leave are so high then they are able to retain most of their long term members , as well as converting enough children and "interested ones" to grow , albeit at a slow rate.
Other religions may also evangelise and use social media , but perhaps this just masks / offsets a greater "churn" of members. I know a local Pentecostal church which uses lots of social media and runs a food bank and a childrens nursery ( as conduits to ostensibly do "good works" , but really to try to bring in new members ) etc but hasn't really grown overall in numbers as people come and go.
I spoke to a friend who used to be involved and he just said that he kind of got bored with it and the politics and constant demands on his time and for donations so he just quietly checked out and he knew many others who had done so. He described the process as just like not renewing a gym membership.You don't really have that easy option as a JW - even fading is really difficult and has often severe consequences in terms of shunning etc..