Well they did exactly that - rewriting the Finder in C++, etc.

But it's unfortunate that losing Pascal/Object Pascal also meant losing bounded strings and array bounds checking, even if people turned the latter off in the 1980s because they thought that the performance cost wasn't worth the reliability improvement. That was probably the wrong trade-off then (at least for most regular application code) and even more so today (especially for the vast amount of legacy C code.)