The reason I'm confident that the old Roman cults are still around is because they were the centres of power which drove the functions of society. As we share a very similar model of structuring society, it stands to reason that these centres of power WILL exist, and so anyone who desires to control society and prevent it from descending into chaos, will need to make efforts to control these centres.
Essentially, the building couldn't be there if the foundation wasn't intact.
Do be careful how you consider approaching the subject of major cults. They exist because they represent the best way humanity has yet come up with to address a specific segment of the human experience. If you seek to disrupt their operation, you had best be prepared to present your own answer to the problems they labour to resolve.
Hey man, I'd much rather not be dealing with any of this shit, but some geniuses decided to shove the entire world's population into the same room together all at the same time with no clear plan.
They seek to create a false world to rule over, but the rug pull in the last act is that it's only possible to create the proper world.
You can try many path ways, but eventually there is only one.