This is the movie I most actively dislike.

Rating: 1/10 (27 December 2018)

Basically everyone involved decided it would be hilarious if they just phoned it in really hard, and felt that their celebrity and ABBA would make it okay. It did not.
Being a musical is not an excuse for terrible dialogue. Being campy isn't an excuse for ubiquitously awful ADR. Him being a celebrity is not an excuse for casting Pierce Brosnan to sing and attempt an American accent. Being the most respected actress in the world is not an excuse for Meryl Streep to phone it in. Being a stupid movie is not an excuse for everyone involved to not try.
I'm torn about calling it the worst movie I've ever seen as a matter of the end product, but it is the one I hold in the most contempt. Nearly every other movie I've seen (including many a MST3K worthy outing) has given me the impression that most the people involved at least put in a workmanly effort, and usually that many people tried their best, to make it good. If one takes "the Room" for example, although the film is objectively terrible there is a sense that those involved are doing their often-pathetic, sometimes-deranged best. Even going down to detritus like "Manos: the Hands of Fate", many of the largely talentless local actors involved seemed to have been very invested in being in the movie and gave it their all.
In "Mamma Mia!", with minor exceptions (Christine Baranski, for example, played the exact same part she always does and always does well), everyone involved in this clearly had a lot of fun using the campy, fun feel of the film as an excuse to not do their jobs competently. It is a black stain on their resumés so far as I am concerned, and I'm sorry ABBA, I now associate your music with purposeful mediocrity every time I hear it.