Just chiming in to tell my disastrous experience with the deprecation of Classic Sites.
A few weeks ago, we activated GSuite for our organization, and from then on could no longer access our Classic Sites. After a long and confusing support chat session, it turns out that our Classic Sites were simply wiped without a warning when we activated our GSuite for the same domain, because of a bug due to some funky deprecation-stuff of Classic Sites.
So yeah, we're pretty pissed that us subscribing to another Google product caused our old stuff to be deleted because of a bug. But it's not that surprising given the rush Google is apparently in to deprecate Classic Sites.
Oh, and I don't think Google's gonna take the time to fix this until the final ditch, so be wary if you still have Classic Sites and are getting GSuite soon!