if thats the case it's definitely not consistent, as i often do this and only get lower gear occasionally. How come they made this change?

It is consistent and has been for over a year now. So the only answer is that you're inconsistent with what challenges you do on which characters on which days of the week. Also keep in mind some rewards always drop higher than others. Not all Powerful Engrams are the same. A daily challenge engram will only be 1-2 levels above your overall power. And in any case you might get something that's lower than your overall power but higher than a particular armor or weapon slot that is holding you back. They did this to prevent people from power-leveling in 1/3rd the time, which created problems with content longevity throughout D1. People rush to get to max power asap and that's not good if you can do it in a matter of days after a new update.