Google does deliver updates but their Nexus devices are firmly in the unimpressive camp and sometimes downright suck. Remember, these are the flagship devices for the entire platform.
2015 actually delivered an exception to the mediocre Nexus phone rule with the Nexus 6p. But that's only viable if you want a large-class phone. The Nexus 5x certainly falls into the suck category.
Maybe Computer Science should be in the College of Theology. -- R. S. Barton