Question for our coaches out there

[Hunter Green]

I realize philosophies change over the years on both sides of the ball. It's the nature of football. I have noticed a trend at both the college and pro level where a defensive back, when in tight coverage, does not seem to locate and make a play on the ball. When I played, way back in the day, our coaches taught us to run with the receiver and  when he turned back to look for the football, the defender should turn as well in order to pick or break up the pass. I almost never see this done very much. Do they not teach this technique? Seems they mainly face guard or just watch and let the receiver catch it. Am I wrong on this?