I know plenty of people are using other metrics like DA, PA, TF, etc. I do myself.
The bad thing about PR not being updated is that PR gave these other metrics a benchmark. These metrics are trying to give us some insight into how Google sees pages. When PR was updated, they could always look at that to know if they were on the right track or not.
If there are no more public updates, as Google makes changes to how they calculate PR, these other metrics will become more and more inaccurate, unfortunately.