There has been drift, introducing problems, e.g. no earths and metal switches, but that's a very different situation.
The situation is no better here. You have no recognised fault protection on the cable. Granted changing the switch won't make the installation worse, but it's a matter if integrity.
If you're asked to replace a lighting circuit with all new cables except the switch drops 'cause that would ruin the decorating, would you accept it? What if those switch drops had no CPC and metal switches hanging on the end?
If someone asked you to replace the plug on an appliance but the sheath was missing on half the cable, would you be happy to do this? Would you expect your scheme to support your decision if you did?