There are lots of website quality stats that you can check to see the quality of a website; Moz, Majestic, Ahrefs, SemRush all have their own set of proprietary stats but you can also use backlink profiles, social shares, domain history.
PR is still a usable metric though IMO, just that it isn't the be all and end all that it once was. Used in conjunction with other stats it can be a useful metric.