Google Maps is a mature product and innovation seems to be lacking with it. In other words, it's like every other Google product. Here are a few things Google could add to Maps to make it more useful. I believe Google has the data to implement all these ideas now.
Maps has no sense of risk tolerance. If you live in a high traffic area there are roads that you know are high risk. If all goes well the drive is 3 hours, but it could also be 5 hours. Meanwhile, an alternate route is 3:45 with little risk of a delay. Google should have the data to know this, and the maps interface could rate routes by riskiness, allowing the user to choose routes based on their own risk tolerance or how much of a rush they are in. In the scenario above I'd take alternate route every time. BTW, that is not a made up scenario. That is basically Fredericksburg VA to VA Beach, with the risky route being I95 to I64 and the safe route being US 17. I always took 17.
Today, toll road routing is either on or off. Similar to above, Google has the data to give you an option to take a toll road by telling you how much time it'll save. Then you can decide if you want to spend the money. They could probably put a threshold in the settings so that it takes the toll road anytime it saves you X minutes.
Scenic Route suggestions
Most of the time, people go from A to B via the quickest route possible. However, Maps could alert us that there is a scenic byway in 5 miles that will add 8 minutes to our trip if we choose to take it. I'd take that detour frequently.
Interesting side trips
Likewise, Google knows what we like based on our search history. Maps should be able to point out that because you often search for yarn related stuff, you might be interested in the world's largest ball of yarn, 18 miles west off an upcoming exit. Or, knowing my taste for BBQ it could point out there is a highly rated BBQ joint 20 miles ahead, and hey, it's lunchtime.
In short, Maps could use Google's data about us to actually make our lives better.