That seems to happen a lot on long running shows. Especially sitcoms. Characters start out relatively normal and as the show progresses they become wackier and more like a caricature of their former self.
"Notice how I ride side saddle, it proves I'm a lady of quality."
Witch Hazel

Actually, I always thought the character evolved a lot. In the early seasons, she wasn't happy with the rich life, probably because she didn't want to be perceived as an Uncle Tom. Once she got that job working at the Help Center and helping others who were poor, she felt she could enjoy the rich life more because she had not turned her back on where she came from. That was the key, I believe.

The show did evolve over time, yes, but that is the way a long running show is. I didn't have a problem with the later seasons too much. I don't believe that the actors complained about the scripts-Isabel and Sherman certainly didn't complain about the first Fresh Prince appearance they did, which was awful! Now if I had been them and read that, I would've told the writers, "You don't know how our show was. Probably never watched an episode. We aren't like that. You have to change this or I'm not doing it."

I think the only one spared was Helen who pretty much remained normal throughout the series. I was just a kid when it first ran on Sunday nights (born 1970) so I didn't really notice the changes then.
But now when I watch it's just glaring how different they became as time went on and I wonder if the actors themselves cringed when they opened the new scripts for the week.

And if you think Louise got dumber, just take a look at Tom. He's a complete idiot obsessing over food and playing the foil to George.
Al - Alicia
An - Andrew
Jo - Joseph
Be - Benjamin

Yes, they definitely messed up her character. I noticed it when I watched the show first run.

I think it's just that the later shows were made so silly thanks to those two
Married With Children
clowns