It's a combination of an underpowered (by 2015 standards), really long-in-the-tooth processor underneath (an nvidia Tegra 2 from circa 2011) and a very ordinary browser implementation.
While the browser implementation can be redeemed a bit with future software updates, the hardware update/retrofit will be a bigger deal, of course.
The browser is the only truly embarrassing part about the car. When I demo the car, I always state a disclaimer first about the poor browser. I'd rather hide the Web icon if the UI lets me.