You're forgetting how much the mass audience's (including critics) appeal over dramas is quite poor.
"The Dark Knight" was a movie that, at its time of release, would not have made the same success without Heath's tragic demise, because it was essentially a crime drama featuring Batman, Joker and Two Face.
I remember leaving the theater kind of depressed by the movie, but I never would have dare call it a bad feature.
Now, go look up RT scores of all crime dramas released in a year.
They're always generally treated very poorly, because they don't have mass appeal.
For example, "Blitz" starring Jason Statham, a very dark movie which had a scene so violent I had to turn it off, stands at 6.2 on IMDb and 48% on RT with an average of 5.1/10 from critics and 36% with an average of 3/5 from audience.
Does it make the movie an objective disgrace?
No, I wouldn't dare judge it like that.
Technically, it's done very well, it's just not a family movie.
I might actually give it another chance when I'll be in the right mood to rewatch it.
To conclude, the market is now geared towards the Star Wars/Marvel packaging, but WB tried the same thing with Green Lantern and the audience responded badly, so how can you blame them for going the MoS/BvS route?