It’s still an assumption. AvP came out around that time and didn’t go that crazy with the CGI, and they easily could have. It also wasn’t that bad either. Just because Lucas went nuts over the SW resurgence doesn’t mean Reitman would have, he has been fairly consistent with his inclusion of practical effects…

Who says they wouldn’t have also used practical effects for a good portion of the designs, like they did in the first two movies. That’s a little presumptuous of you.

Murry and Ramis were speaking to each other well before his death. They had made up some time ago but were no where near as close as they once were.…

They went out of business because the city sued them for damages and disgraced them, it’s also implied that there were people that believed the Busters staged the whole incident and were frauds. This was made pretty obvious when Ray and Winston were at the birthday party.
It wasn’t a matter of no ghosts to bust, but…