Location of the tabernacle in Catholic churches?

This is not just a church architecture question but also a theology question. I've noticed that the tabernacle where the consecrated hosts are stored is often located in the center of the older Catholic churches, behind the altar, so when you enter the church, it is a focal point. But in more contemporary churches, the tabernacle is somewhere else and instead when you enter the church you see chairs where the priests sit. I would like to understand why this change occurred. Was there a change in theology? The message the newer layout sends compared to the old is that the priest has displaced the tabernacle. Surely that can't be the intended effect?