As far as I can recall, Betty White was the last living person to have served as host of an episode of Password, after she and Allen swapped places during the ABC run.
The only household-name level shows that come to mind that have had multiple permanent hosts over multiple non-consecutive runs where none of them are still with us are What's My Line and, for a few months in 2020-21, Jeopardy.
After that I start getting down to shows like Blockbusters, which meet the criteria I set but don't feel as significant. Is there anything I'm forgetting?