From October 2003 (https://web.archive.org/web/20031012104730/http://www.tvtattle.com/):
https://web.archive.org/web/20031012104730/http://www.suntimes.com/output/rosenthal/cst-ftr-phil30.html

"What once was outré now seems passé, no longer daring, almost retro," Phil Rosenthal says of Bunker-esque sitcoms like "Whoopi" and "Luis." "What used to be satirical, eye-opening and genuinely funny is now simply played for straight-on laughs and, even unburdened of nuance, it tends to fail. What we're finding is it's one thing to have a Bunker mentality and quite another to have Bunker's thinly veiled angst and frustration at the slow realization the world is passing him by."

It's a pretty simple answer, the same reason you can't recreate most classic shows.

You had a magical cast, the right story that came along at the perfect moment in time. That can't easily be duplicated.