9 million is a very conservative estimate of the number of JWs because most other methods of counting find far higher numbers of JWs. For example Watchtower claims only 1.2 million JW publishers in the United States whereas the US religion census cited above found 3 million JW adherents in the United States. The same pattern holds in other countries where censuses regularly produce far higher numbers of JWs than the official publisher count.
The congregation that I attended for over 30 years is gone now, dissolved, and no, a new congregation was not started as some Witnesses would have you believe. Attendance got so low at that congregation, and at a second English congregation using the same hall, that they had to be combined. This is happening all over the world.
The number of congregations has also increased significantly since 25 years ago. There were 90,000 congregations in 2000 and 118,000 in 2024. So while some congregations may not have increased and multiplied this is the overall trend worldwide.