Those exist. The Win32 Common Controls libraries are versioned and applications can opt in to them with rebuilds. There are also "application manifests" where in some cases an EXE can claim that "I know I was built with an earlier version of Common Controls, but I do the right things with them and was built with forward compatibility in mind so please display them the newer way".

The problem with opt-in flags is that it still requires active application developer work (keeping up to date on dependencies; sometimes worse, keeping up to date on future dependencies and learning their restrictions needs) and still can't solve the inconsistency issues from applications developed by people that don't exist anymore or don't have a maintenance budget or the source code was lost or…