I use GHL and lots of my clients do as well. Not a scam, although the affiliate program an attract lots of gurus. The system is pretty solid And can definitely scale and add value, at the end of the day it’s all about how you fullfil as an agency, not just the bells and whistles.
Don’t underestimate #4. It’s not easy to get people to sign up to a whole new system/site. OF is a known entity. Plus, running an entirely new business (software business) is not easy. Several of the celebrities that have done this are B-listers at best, not always the most informed/managed and good with money. Real A-listers steer clear and don’t want to be associated with that brand.