Why did Jo Marie Payton leave this show?

They intended to renew the show for one more season, and they didn't allow Payton to be included in the creative process, despite that the show was originally supposed to be hers, and the show really did stray far away from its roots and revolved around Steve Urkel far too much.

She wanted to write a few episodes to try to restore the integrity of the show, but when they didn't allow her and continued to bank on Steve Urkel, she just quit.

If they knew that the ninth season would be the final one, she might have stayed until the very end. But in the end, the show got canceled.

She felt the show had jumped the shark. She wanted to leave a few years before she actually did

FAMILY MATTERS: A TALE OF TWO HARRIETTES

https://www.youtube.com/watch?v=IfC9SgMV2TM

From Perfect Strangers to Family Matters, Harriette Winslow was an integral part in the TGIF line up. She was a loving mother, caring wife, and a quick witted sarcastic one line machine....
And then shockingly halfway into the last season of Family Matters, she was randomly replaced with a brand new actress.

I heard she just wanted out. The show had been going for a long time by the time she left.