To be fair, MoS wasn't trashed, but was sharply divisive, and it's average rating on RT is right in line with the average rating of a good chunk of MCU movies. The audience reception is also majority positive by a decent margin, despite all the internet arguing about whether Superman should kill or not would have you believe.
The major problem is that instead of leveraging MoS and following it up with a feel good movie that isn't seeking to re-invent the wheel or seek controversy, they went with a movie that is among other things a veiled attack at the critics of MoS and deals in depressing subject matter and is oppressively dark, albeit it has its reasons for being so (it's called dawn of justice for a reason). And on top of that you have the issues regarding a movie missing 30 minutes, and out of place JL teasing shoved in at what seems the last minute, creating an incoherent theatrical cut to make matters worse. The lead in concept in DoJ is a much more natural segway into a shared universe, and there was no need to shove all the teasing in before...but oh well.
(spoilers)
