[tkoolen]

The fact that these transitions were so painful doesn't mean that all breaking changes have to be so painful. With Meyers' 'magic wand', the transition is eased quite a bit. But another important component of a smooth transition is a 'carrot', a new feature that's so compelling everybody will want to move to the new use the new version. If a C++ with major breaking changes would also halve compilation time for example, most people would switch in a heartbeat.

[jonex]

That assumes that compilation times is a number one prio for all users. Halving compilation times certainly is worth something, but the cost will have to compare well to other options of reducing compilation times such as using distributed builds etc.

In the end it's really hard to force breaking changes for systems that are working sufficiently well. If I have something that I'm satisfied with (after all, I chose to use C++ over Go, c#, D, Ada, Pascal, etc., why not choose C++17 over some hypothethical incompatible C++22)