There is actually the opposite problem now with Google Maps, where you'll be traveling happily on a route and it will tell you "we found a route that's 20 seconds faster by taking you down a road you want to avoid, take your eyes off the road to press a button on your phone immediately or else we're swapping you to it!"
And even if you're at a place where you can safely hit the button, it keeps trying to do it over and over again every time you pass a new exit that can take you to the new route it's trying to foist on you.
As far as I can tell there's no way to make it opt-in, configure it so that it only swaps you if it's a big time savings, or turn it off completely. The only suggestion I find online is to turn off mobile data which means that you then lose real-time traffic updates entirely.