Sorry Dell but Modern Standby is broken by design by Microsoft.
Disconnecting wifi may or may not help.
Also in Disconnected standby, Windows OS or drivers or modern apps may choose to do something they deem important, either preventing the laptop from entering the lowest power DRIPS state, or causing the laptop to leave it. Which the user may not want, for the sake of the battery power drain, or overheating while in bag or such (very bad for batteries which are prone to swelling etc).
Debugging (Sleepstudy) in involved for average users, and eventually they have no option to easily disable anything, except for uninstalling potentially discovered "offending" apps or drivers (unless system).
This is originally not Dell's fault, but Dell should at least allow one to switch back to S3 in BIOS until Microsoft fixes S0 so that it is at least as good as S3 in aspects of battery drain and bag-safety, the way Lenovo did.
There is no point in the new CS allowing the devices to wake 2 sec quicker, if one actually has to use Hibernate instead, which happens to take half a minute more!!!