YOu simply can never go back--what made originals appealing were due to a combination of factors unique to a certain point in time and in the viewers' lives. That is why so many resurrections/reboots fail. Viewers think they would love an old show to come back or have a reunion but it never is the same and they are left feeling like it would have been better just to leave the series dead and have that pining but it never being fulfilled.
It also doesn't help that they usually just have the old cast as props and not the focus.
It also doesn't help that they usually just have the old cast as props and not the focus.