I think if you tried using gmaps for navigation you’d find it to be a far superior to those devices. Does your TomTom tell you “turn into the driveway after the Vitamin Shop”? Because gmaps does.
And Garmin units have had natural directions like that for four or five years. But I find it more of a hindrance than anything. I would rather hear "Turn right onto Wellington St" than "Turn right at the Starbucks", especially because the Starbucks is not always obvious.
But more importantly, I prefer a dedicated device because it's way more convenient. It's always there, it doesn't kill my battery, it doesn't rack up roaming fees when I cross the border[0], it has a large screen that's easy to see[1], it has super useful features like "Up ahead" that shows where the next rest stop, service centre, etc. is, and it leaves my phone free for audiobook duties.
My Garmin has been nearly 100% reliable because it never moves and automatically comes on with the ignition. Google Maps is at best 20% reliable because it's not there when I need it.
[0] Yes, google Maps can download maps to work offline, but they constantly expire, leaving me high and dry when I actually need them, and I don't want to download half the continental US just for a road trip. Oh, and POI search is gimped when offline.
[1] My phone does not have a large screen, and Google Maps' map is incredibly difficult to decipher when driving because of super thin low-contrast lines, tiny labels, and a non-zoomable display (when in driving mode).
If flawlessly defined sending one to the closed street and putting one into a two hour long traffic jam because it has no real time data feed, then sure maybe it is flawless. But this is 2019 and not 2009.
Furthermore, it does have a data feed for traffic, through FM radio (using the power cable as an antenna) and/or a Bluetooth connection to a phone. It's not as good as google Maps' traffic updates and it's only for major roads, but it works pretty well.