The responsibility for the safe conduct of the flight lies squarly with the commander of the aircraft. After all they (ATC) are not going to stop and search you or ask for your licence number before issueing you with a clearance.
Less scrupulous aviators have been know to abuse this; no doubt their insurers will catch up with them on that bad day!
So if you with a vanilla PPL accept vectors in class D and get vectored into some juicy clouds you are to blame nobody else.
So in doubt make clear what you can and cant do.
FD