He'd have been written by Morrison with pretty much everything from Superman & The Authority. I don't see that as shitting on him.
I think it more gave soft ending to them that acted as honest critiques of how superhero comics stagnate and ultimately become more about their navel gazing than leaving the world better than they found it. Morrison likely used that general critique as the base for Superman & The Authority, and it's why that's how he opens things with Black-- by saying he and his friends did in fact fail.All the plans I've read about 5G generally threw away the past to build a future, but i would argue having a very out-of-character and unsatisfying ending to the OG characters like right wing authoritarian Superdespot was more harm than good and destined 5G to be another thing to retcon.
But the thing that people who write 5G off seem to be missing is that wouldn't have been the end of their stories. Similar to how the JSA being forced to retire didn't end their stories. As stated before, the OGs would've basically taken on a JSA role, and that means they've have had room to grow and teach. It's like assume the New 52 starts and stops with the Justice League not being friends or Superman not being able to fly. It's an arc.
With the above in mind, I think that's being dramatic.You can't just light the stuff people like on fire and give them something else thinking it's going to be okay if they like the new stuff too.