I am not absolving WB execs of blame, but Whedon didnt just do his job, he did a bad job.
I understand that he had to cut the movie down to 2 hours. Ok fine. But he shot MORE stuff and shoehorned it in place of awesome shots like the one giffed above.
For example, the Darkseid vs old gods scene is around the same length of time. But its got almost 2 minutes of extra footage of Bruce and Diana walking around and talking for some reason. Whereas, Snyder just does a voice over and takes the time to set up the scene. You get to appreciate some action scenes instead of them just being cut into a montage.
vs this
The scene where they decide to bring superman back to life is also so much better in the new version. They discuss what the mother boxes can do and then without anyone saying it, all decide to bring him back. Cyborg makes an awesome looking hologram, the man of steel theme plays and you get an awesome shot of Bruce Wayne looking at Superman soaring. Whedon added a bunch of nonsense with Diana shoving and punching Bruce. Same runtime. Different scenes shot poorly. This is true for pretty much all of the movie. No idea why so much of the movie had to be reshot.
I'd still personally blame it all on WB. IMO Joss Whedon can make a good film, I think both Avengers 1 and 2 are really good. The only crap thing about Avengers 2 is Thor going to that water place to get visions but that scene was mandated by the higher ups, probably higher up than Kevin Feige.
The Steppenwolf/Darkseid versus the old Gods scene is amazing. But they probably truncated that scene as the funding that was required to finish the longer scene went towards the reshoots mandated by the studio. Scenes were re-shot based on tone, a tone mandated (again) by the studio.
Regarding the scene where they decide to revive Superman and they play the theme from Man of Steel, the whole soundtrack changed from Junklie XL to Danny Elfman. Now we don't know about any of the contractual obligations concerning the music but they obviously couldn't or chose not to use any of Hans Zimmers music from Man of Steel and without his music that scene would not have had the same impact. WB wanted to spend X amount of money on music and they didn't want to pay extra for Hans Zimmer.
Again, who knows what the fuck WB were thinking in regards to anything for this movie.
At the end of the day, WB really fucked up Joss Whedon's career even before these allegations came out about him. Joss Whedon can only blame himself for making that decision though.