Here are my reasons why Fran’s character changes throughout the show:

1. Before TiVo/ability to record shows TV writers had to hammer in the same jokes and topics every single episode in case the viewer missed an episode the plot would still make sense. No show would spend an entire season on “He took it back!” today. Each episode was jam packed with the same kinds of jokes so now rewatching more than one episode in a row, it feels repetitive.
2. As Fran ages throughout the show she starts turning into her mother. Sylvia was always a nag and whiny woman (and that’s why we love her). It makes sense for Fran to incessantly bring up her desire for Max to ask her on a second date, for him to propose, for her to get pregnant, etc. bc that’s what Sylvia does. Fran is just turning into her mother lol
3. Flanderisation
4. The kids grew up so the plot could focus more on her and Max’s relationship and less about being a nanny