I largely agree, and it is disappointing to know that there are now more bad seasons of The Simpsons than good ones. A child born today has a greater chance of someday stumbling across a crappy episode and having a negative opinion of the whole show, and that's sad. But that doesn't mean it's not worth showing those children the first nine seasons.
There are caveats for both sides. Those that say the show is an average sitcom overall should still point out that the first nine seasons are amazing, and those that say it's one of the best shows ever made need to point out that the show went on way, way past its prime.