There is nothing wrong with the UI, or even the choices that you're offered in this science-fiction thriller. The flaw is more fundamental than that. It just has terrible characters.
First of all there is a fundamental difference between a sci-fi story and a horror story. In horror, morally corrupt characters are punished for doing "sinful" things while the final character, who is somehow morally superior, survives by overcoming their fear. In sci-fi, people overcome a problem because they are competent and intelligent, and if people die, it is usually because they didn't listen to the scientists. Sci-fi horror is usually a blend of these two concepts, where the sin is not listening to the science. A thriller is just a story that starts with a dead body and has lots of twists.
While The Complex manages to nail the thriller aspect, it fails at both horror and sci-fi. The scientists make stupid emotional choices and hardly use their decades of knowledge to solve problems. One character has magically gone from being an epidemiologist to being a hacker. And the plot is entirely lacking in moral nuance. The "bad" guys face no negative consequences for either amorality or bad science. I was kind of kept in it by the possibility of making a choice that would stop the train from derailing, but I never felt like there was actually a choice that truly used either cleverness or morality to assert some sort of complex outcome that would have changed the character's perspective.
Consider the first choice you make in the game. Do you:
A. Save a dude who was playing soccer
B. Save a pregnant woman who might also be a freedom fighter
This is not a choice. There is no moral quandary. There is not even an intellect vs. emotional choice here. A better one would have been saving the leader of the opposition of a tyrannical country, or saving a CHILD who had been playing soccer, with his family waiting for good news outside the tent. The Complex has a good setup for storytelling, but somehow passes right by it without blinking.
If you like a Patterson story, though--a pure thriller, and many people do like that enormously for good reason--then this is a good story. It's up there with The Zoo, where people in labcoats make decisions any one of us could make without even getting a degree or building a global business. It's not my thing, but if that is something you enjoy then don't be intimidated by the sci-fi/outbreak presentation, this is comfortably mainstream and not for me.