Pretty much this. Rebirth was needed after the New 52. Sorry, but Dan Didio’s vision for the DC Universe just didn’t work. At all.
It’s one thing to say “we want to bring in more new and diverse readers and reflect that diversity in the actual slate of heroes we publish.” That’s something that should always be strived for. However, it’s another thing entirely to turn around and say “and we’re going to do that by wiping away almost 80 years of established lore and/or continuity.” That...rightfully gave people some pause. Even if the end goal was admirable, the execution really wasn’t. A lot of the stuff that came with the New 52 was either not reflective of diversity or just wasn’t particularly smart in how they chose to incorporate more people of color into the DC Universe. I think we’re all well aware of how their attempt at introducing a black Kid Flash was a train-wreck in that not only did it irrevocably alter a fan-favorite character but also turned that fan-favorite character into a stereotypical “street kid” who needed Barry “White Savior” Allen to put him on the right path.
On top of that, it ERASED a lot of the POC characters that existed in the DCU prior to Flashpoint. It’s also of note that Marvel accomplished what DC sought to accomplish WITHOUT rebooting their universe. But, all of that’s been said before.
And while Rebirth itself was a much needed breath of life back into DC, it still fell prey to a lot of the things the New 52 did: behind the scenes drama. Lee is right. For too long, DC has been subject to editorial mismanagement. No offense to the guy personally, but Dan Didio was not a good publisher. He constantly interfered with and alienated creative talent and pushed storylines and events that were questionable at best in terms of quality.