From what I have heard and seen, the halls are emptying not at great speed, but for Jehovah's Witnesses who are always accustomed to growing and building new kingdom halls and forming new congregations it is a great blow and defeat.
The situations are patchy, but in general just look at the official numbers: congregations are decreasing, baptisms are decreasing, 70% of them are children born in. But obviously we still don't have the decline of the Catholic Church because we have the elders who watch over the flock and keep them in line. It's not just Zoom, there's a lot more awareness that the JW system no longer holds up and people are leaving or cooling off. We have recently reinstated 3 disfellowshipped brothers, but 4 elderly brothers have died, and no one has been baptized at the assemblies for at least 4 years. Nearby 2 congregations were closed and merged with others. There is no growth but a slow emptying and there are no new ones entering, very rare.
Also in my congregation we have 3 new inactives, and in the congregation next to ours, two families have dissociated themselves by sending a letter with the reasons