Honestly, this has been a topic I’ve been thinking about a lot this week.
For me, media res is often jarring. It can be done well, but is so replete in novels/visual media, that if an author does it I’m normally turned off.
There are also other variables I consider, as readers are more willing to accept a premise they are already familiar with, rather than take a chance on new terms and a new world.
I enjoy a healthy amount of world building before the action starts. Otherwise, at least to me, it’s hard for me to get immersed in the world.
Like Zombie Exodus I could jump right into, given that I knew the tropes or at least the basic premise. I was more willing to give the long customization a chance since I knew the outcome would be satisfying.
On the other hand, many science fiction ,fiction, or fantasy stories have long intros or due to attempting to set up a world. People may be less willing to give a longer intro/customization a chance, due to not having any expectation of how the rest of the story will unfold.
Long story short - it depends on who your audience is and what type of story you want to tell.
I weave long sagas, and have a long attention span. A few paragraphs and then action jolts me. A decent intro, some moral choices, and I can get hooked.