Sins of Youth was a good example that the Young Justice could take over one day...
You CANT compare them with Conner,Cassie,Tim etc.
I always thought that Diana and Donna are very similar with Donna being the one with the better attitude, so it wouldnt make a great difference.
Dick works better as Nightwing and he is always the friendly guy..
Tim is a VERY DIFFERENT character and his Batman is very dark...
Tims Batman is more interesting than Dicks Batman, because Tim has a very different personality and is for example more like Bruce, but even being darker..
We saw Conner as Superman in Sins of Youth, Titans of Tomorrow and as Black Zero.
All 3 versions worked perfectly and the ToT Superman was actually very cool, his fight against Shazam (Freddy) was interesting because he showed that he can shield himself from magic..
Conner,Tim,Cassie...work better in the role of Superman,Batman,Wonder Woman than Donna,Dick....
No!!!!!!
The ONLY real problem is only the TIMELINE.....
Legacy always worked perfectly (FLASH,GREEN LANTERN,ROBIN,...)
And to have success the character also needs development, storylines, feats etc.
Dicks Generation was LUCKY because they got cool new names and development (Nightwing,Tempest,Arsenal,...) while Tims Generation uses still the old Codenames and would need to be aged up and get new codenames...