The navigation system in the Pacifica is better than average for automotive systems, but there is no automotive system (built-in or add-on) as good as Google Maps or Waze.
Whether the UConnect Nav is good enough or not depends on how often you use it and what you use it for. I live where traffic is usually the biggest factor in route planning and I value truly real-time up-to-date traffic over any other aspect of navigation performance. I love the crowd-sourcing aspect of Waze but let's face it, it's really a data collection and adware platform. If there were a "pro" or "premium" version that you could pay for and avoid the data collection and ads, I would pay for it. I find Google Maps to be less offensive in that respect (or perhaps just more subtle), and it uses crowd-sourced traffic data from Waze, so that is my go-to navigation app.
The built-in UConnect Nav will get you to your destination, but it won't necessarily get you there as quickly and efficiently. The traffic info that it obtains from radio is not as current, time estimates are not as accurate, it sometimes takes you on odd routes or makes you backtrack, it's database will become out of date over time and you'll have to pay to update it. Compared to my phone, the navigation map display is sparser and less informative at an equivalent zoom level, and panning and zooming the map is pretty slow and unresponsive. Voice command recognition is better than most automotive systems I've tried, but it still falls short of Google or Apple or even Samsung.
The only advantages of the built-in navigation system are the ability to show driving directions in the middle of the instrument cluster, which is nice, and you don't need to find a spot for a phone mount.