It is not so much the flagging of dependencies, but knowing what they are.
For example, I am Mono averse so I want to know before I install that it
includes Mono so that I can avoid it. That is not the only thing, but it is
just an example. Software Center and the Muon equivalent do to present it
in the detail that Synaptic does. The Muon SC does not even mention Mono.
Instead it gives rave reviews and shows how many stars which I could not
care less about.