Why wasn't Theo spun-off into his own program

In 1992-93, a year after The Cosby Show ended, Malcolm-Jamal Warner starred in another NBC sitcom produced by Bill Cosby called Here and Now. It only lasted for a season's worth of 15 episodes (the last two were never aired on NBC) and Bill Cosby himself said that the cancellation was justified since he felt it wasn't written well enough.

But my main question is that why wasn't Here and Now simply a Theo Huxtable spin-off and would it been more successful had it played up the Cosby Show connection more? I mean, it wasn't like Malcolm-Jamal Warner wasn't playing a character too far removed from Theo anyway.

Was it not turned into a full-blown spin-off because they already tried and failed with another one of the Huxtable kids with Lisa Bonet/Denise and A Different World?