Is Poirot the problem in recent adaptations?

Like many people, I do not like the Kenneth Branagh movies. I don't connect to the cinematography, to the heavy ambiance and to the casting.

At first, I thought it was because I do not like known actors as an assemble cast, I find it distracting from the plot (I have the same problem with the Benoît Blanc movies).

But recently I watched two of the Peter Ustinov movies and despite not being used to him as Poirot and a known assemble cast, I enjoyed myself. Then I watched the beginning of ABC murder with John Malkovich and I didn't enjoy it.

And then it clicked.

In those adaptation I don't like, Poirot personal situation is the center of the story. It's about his backstories, his losses, how people perceive him. It's how the mystery connect to him, one way or another.

And that doesn't sit right with me. Agatha Christie write about human nature, social connections and murder. But Poirot is the medium to witness those, not the center of it (unless we are talking about his own end, which is a specific case).

The screenplay of ABC Murder was written by Sarah Phelp, who also did And then there were none, which I enjoyed a lot : known assemble cast, no focus on a primary detective.

So now I wonder : could the problem be how focused on Poirot the story is, instead of the mystery itself?