I think at the point they made Ghostbusters: Answer the Call, an actual sequel had fallen off the table with Harold Ramis's death and Bill Murray's constant lack of interest. At that point, reboot (with cameos to incorporate the original cast rather than having them reprise their roles) seemed a reasonable thing to do.
More like an Hollywood thing to do. I’m still of the opinion they shouldn’t have waited for Bill Murray to make a Ghostbusters 3. This idea that people become fan of a franchise as nothing but a pile of names is why we got NuTrek instead of just continuing that universe, it’s why The Force Awakens was just Rebel VS Empire with the numbers filed off, or that Hasbro keeps putting out a crap ton of Bumblebees… or how we got Ghostbusters II in the first place.
If you look at what the Ghostbusters hard core fans have been doing, that is to say create their own Ghostbusters chapters all over the country and even world, you’d realize there was more to the franchise’s appeal than Bill Murray, Dan Akroyd, Harold Raimis and Ernie Hudson (though Hudson got shafted in term of exposure and could have used more focus) and that obsessing over THESE FOUR GUYS meant we lost Harold Raimis before he could be Egon again and cost the franchise a lot of potential development. Imagine if they had just given an excuse for Venkman to not be there, use the third movie as a way to introduce more characters and kept going with a mix of old and new… and then at some point Murray might have come back on his own and then it would have been a big event. The Franchise could have been a big moneymaker if they had decided to develop it as a coherent universe.
Answer the Call didn’t need to reboot the franchise to star four women, nor to attract fans old and new.
This new movie looks primed to hook a new generation of young fans and I think if older fans bring their kids along, it’ll probably be spawning sequels for a while.
Now, just don’t obsessed over JUST those four characters…I think franchises who are willing to experiment a bit with their basic setup do better in the long run.
TL;DR: A franchise's appeal resides in more than just a pile of names.