(1) It's actually rather sensible, because C++ is famous for its backwards compatibility. So you can use C++14 or C++17 features in some new code while leaving the rest as-is - and gradually refactoring some of it with new features.

(2) This used to be the case with C++03 (or C++98), and it changed...

(3) I partially disagree and partially claim you're begging the question. You don't have poll results to suggest what people think of C++14. But - C++14 had a lot less changes compared to C++11 or C++17; this was natural considering how the cycle of debate of potential features progressed.

The thing is, the fact that C++14 wasn't that revolutionary in terms of features also means it is easier to adopt. If you want more novelty - try C++17; or - try a C++14-dependent library like Eric Niebler's ranges-v3.

(4) C++17 allows for writing less complex code in many cases. Specifically, you can significantly reduce the need for template metaprogramming - a particularly hairy part of the language - by using more constexpr functions and if-constexpr in regular functions. And there are other examples. Like Bjarne says: The C++ committee endeavors to "make simple things simple (to write)". So it's a trade-off.

(5) Some people switch languages because of workplace decisions or personal preferences, that's true; but people also adopt C++ because of what becomes possible, or easily-expressible, with newer versions of the language. For example, using the ranges library and with C++14 or later, functional programming with C++ has become quite reasonable, borderline pleasant even.

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Bottom line: In my opinion, at this point C++11 has more inertia than momentum. And that's ok. People will progress over time.