Most organisations are not fully Theory X or fully Theory Y. They sit somewhere in between.
Some rely more heavily on control, rules, targets, and external rewards. Others place greater trust in autonomy, purpose, judgement, and growth.
The same is true of people. Some of us are more comfortable with structure and direction. Others are more motivated by freedom and ownership.
The real challenge is not deciding whether Theory X or Theory Y is right. It is understanding where we are now, what kind of work we are doing, and whether we need to move the slider a little.