In the case of the team moving to a new compiler, what are you suggesting? We can’t merge in use of a newer compiler until there are zero warnings in all our products? Who “fixes” all those code bases? Who touches the pieces of code that were last touched 5 or 10 years ago?

Various solutions are possible, including the obvious one of just removing -Werror. But the point is that this decision should be made by the team that owns/maintains the code, not by some centralized devops group.

Yeah, 100% agree. Or even better, for incremental improvement, have it enforce no new warnings.

But all of this requires adding complexity and branching to the system. It can be done and is worth doing, you just have to choose your battles.