There's more to it. It's not just the ability to be in multiple queues at once, which in itself is an enormous advantage. It's also the ability to join a queue from anywhere in the park, at any time. A standby guest cannot join a ride queue from the turnstiles the moment they enter the park. At MK and DAK, it's a hike to the nearest ride and that walk is in addition to the standby guest's wait, whereas it's included in the DAS wait for the first attraction.
A standby guest cannot join another queue as soon as they reach the merge point in their current queue, where a DAS user can. For some attractions, that's 10-15 minutes before boarding, not including the ride time, exiting and walking to the next attraction. This is why some DAS guests can potentially enjoy the lion's share of ride capacity in any park while standby guests spend that same time navigating the park, waiting in queues up-to and post merge, riding rides, and exiting, etc. It's not just that DAS gives people the ability to be in multiple queues at once, but it also enables them to do all that while waiting in a queue.
The extent of accommodations and power of the advantages the DAS system allows makes it so that if it gets into the hands of those without mitigating factors or those who don't really need it, it can really tip the scales. And it has.
All of which can be used in tandem with or in addition to DAS. These are not DAS alternatives.
This frankly does not matter because Disney can regulate Genie+ in a way they can't with DAS. Disney has more levers in place to be able to manipulate Genie+ inventory to keep lines moving. They can control whether or not the system gets overwhelmed.
Because DAS is not analogous to Genie, it's analogous to standby. A person in a standby line can't be in another standby line at the same time.