Your point about population growth is true. It doesn’t alter the fact that JWs are growing while most other groups are declining. That’s all I claimed and that’s what you originally objected to. Now you call comparisons “simplistic”? In what respect?
As I said above, my claim was that JWs are growing while other churches are declining. I at no time claimed there were no reasons for that fact. Of course there are reasons, and preaching, disfellowshipping and other factors are involved.
At the same time, it’s worth noting that Christadelphians and Brethren also disfellowship and yet they are declining. So disfellowshipping alone doesn’t seem to be a magic bullet for growth.
Most wealthy countries are secularising at an accelerating rate and most churches are experiencing significant declines. In that environment it is noteworthy that JWs have thus far managed to keep growing. I doubt they will be able to defy gravity forever, however, and I would expect they will start declining too, at some point, because the social forces producing secularisation are strong.
I’d recommend Ronald Inglehart’s recent book Religion’s Sudden Decline for an overview of the extent of secularisation in recent decades and the reasons for it.