DH and I had a trip in October 2021 just before
Genie+ came out. At that time, there was a lot of discussion online whether the parks still needed Fastpass+, or if we could just continue to have only standby lines, because Fastpass slowed down the standby queues. (The Fastpass (now LL) lines were used a little during that time, which I know now was
DAS, as well as VIP and guest recovery.)
The standby queues during that trip were awful, with CM's with the sign to where the line started pretty far from the entrance to some attractions. And this is a time when social distancing had pretty much been eliminated from the queues, so that wasn't artificially making the standby lines look longer.
So, I knew then that standby only was not feasible as the parks increased capacity. Genie+ came out a few weeks after our trip.