They're both bad. A perfect example of a rotten remake, The Ladykillers, starring Tom Hanks. It was so over the top and vulgar that it just wasn't funny at all. The subtleness of the original British film with Alec Guinness, Herbert Lom and Peter Sellers was far superior. My wife walked out of the remake after 10-15 minutes due to the overflow of obscenities and by the time I had sat through the entire film I wished I had as well. Shaft didn't exactly have a diverse cast, but I remember enjoying the film when I saw it in college. It was as entertaining as a typical film starring a white guy as a detective.
There was a terrible movie that I remember being released in the summer of 1977 when I was in grad school with nothing to do, a group of us made the mistake of going to see a supposed comedy, Between the Lines, labeled by one critic as "the American Graffiti of the 1970s." It was so lame that I started making remarks out loud from the audience and I was getting more laughs than the film. Finally, we all left after about 15, 20 minutes. We should have known it was going to be terrible, a group came out from the previous showing and everyone was scowling and one woman uttered, "God, what a waste!"
The Blade Runner sequel was absolutely dreadful, far too long with a story line that made no sense, the villain's character seemed to be particularly badly written.
Another example is the most recent CBS Star Trek series, I didn't even make it through the pilot, it was so bad. Glad that I missed the blowhard failure Stacy Abrams guesting as President of Earth in a later episode.
Who is to blame, casting directors, producers, studios script writers?