Now, they might have different wants, and disagree on how to meet their needs, and march off in 800 different directions, but ultimately with enough effort any one group is capable of meeting their own needs.

UI/UX that works well for "normal people" is something that most developers don't understand; they know the UI/UX that meets their needs, but developer needs are quite rarified and abnormal compared to the typical user.

Thus, when they respond to disagreement with a UI/UX engineer by marching off in 800 different directions to scratch their own itches, they end up with no solution that meets the "normal user"'s needs. There's no culture of shutting up and following orders for the greater good of the project.

tl;dr you can't solve the problems of someone different from yourself if the only thing you do is scratch your own itches.