I agree with you.
It is hard to gauge the effects that Dan Didio had on Geoff Johns over time, and vise-versa, but Johns' style and quality did change significantly during Didio's tenure as Publisher. And certainly not for the better.
Without a doubt Geoff Johns' writing style and especially its tone changed over time, and in as much as anything the complete abandonment of established continuity with 2011's New-52 had a very noticeable effect on what it was Johns was putting out as it took away one of the very elements that made him a success in the first place and helped guide his writing - the element of tradition that these characters and books all had. By restarting it all from scratch, and making its distinctly darker in its tone, it took away the established continuity of characters and demanded writers think their approach from the ground up and invent new approaches. In many ways darker approaches at that.
But While Johns landed with the restarted Green Lantern title and Aquaman it would be subsequent work on the Justice League title where his worst traits came to be manifested in my view and his weaknesses exposed. But was that down to the political climate behind the scenes at DC that were directing the New-52 imperative, or was it a willing choice from Johns to seize on the more vicious and grim elements of Dan Didio's approach? The 'Rebirth' reboot seemed to suggest it might be the case yes, but as yet Geoff Johns has yet to demonstrate that his writing has recovered from the darker turn it took under the New-52. But I'm digressing...
I do wonder whether a Didio-free DC Comics, if put under Geoff Johns & Jim Lee's management, might lead to some better stability and a greater emphasis on creative talent being assigned correctly. It may be that Johns is too busy with his role on the Media side to spend the time necessary on taking charge of what appears in print, but either way this is a change I do feel relieved about as for so long now DC has just staggered along as a comics line, repeating the same formulaes and rebooting as the easy option rather than the creative option. Getting a new manager with a new perspective might be the shot in the arm the comics line needs right now. It needs that new vision.
I think the dark D.C. really began with the success of The Dark Knight Returns,Watchmen,and to a degree COIE. Sandman and Alan Moore Swamp Thing could be included though I personally do not think they really fit into the list. Didio inherited that tone and really made it jump into the superhero titles. He is only a part of the system that looks at where the dollars come from then try to find out what worked, bottle it then ride it to death. Reminds me of the disco era. I must admit to spending plenty of time in the disco techs though even I said goodbye albeit sadly
. One of the problem in comics is allowing the past to dictate the future at least in tone and often substance. I am fine with that except not as company wide mandate. Although I am not keeping close contact with D.C. it seems that each reboot actually begins and ends with a darker feeling.
My take on D.C. do or die 5G reboot is just another publicity stunt to scare people into buying more books. From a money perspective it is probably a smart play. Reboot cash jolt juiced up by this rumor will mean big bucks for a while at least. I do not think Marvel or anyone else buys D.C. without the other more lucrative movie and merchandising included and that is not going to happen. Even shipping out the books is problematic at best. If D.C. can not make their goal on finances why would anyone take them since on top of that they would have to pay D.C. just to publish the line? The one thing I can see happening is D.C. using a gimmick to publicize shutting down then re-opening due to "popular demand". From their pov creating a Crisis On Our Earth type situation.
Of course after this posting I remembered we live in the digital age and the companies can and probably will go all in that direction at some point. It would certainly be more profitable for the big 2. This pretty much negates all my arguments above.