From my standpoint, I'm _still_ trying to get my head around all the ramifications of what has arrived in C++-11 (and it's a lot!). And I still have '14 and '17 to plow through too. '20 will be here before I know it. So for me, there is so much to absorb.
To my eyes the C++ leadership has done a great job at setting up standards processes for regularly delivering new versions and the compiler community has done an amazing job at keeping up too.
I expect to see more movement in the world of standard libraries which is where C++ still feels like a desert compared to other languages.
But yes it definitely is not fast when compared to other newer language communities.
The only language today with more independent implementations than C++ is C. Compared to C, C++ evolution is not slow — processes involving so many implementers are inherently not in fast-forward mode.
Most major languages only have a handful of active implementations, if it's not just one implementation. Most don't have specs.
Moving fast (and breaking things) is just not what the standardization committee does, and that's fine. They can move faster since C++11/14, but sometimes you really don't want a giant moving target with new features all the time. I think their approach works for the kind of environment you find C++ used in.
I wouldn't say that it's been great. The evolution of C++ is insanely slow.