I just want to direct your attention to this Dead Homer Society post from last February because it owns:
The Simpsons has been on for so long now that the world itself has changed around them and as a result the characters no longer epitomize what they’re supposed to be satirizing. Homer and Marge are exquisitely crafted late model Baby Boomers; they came of age in the seventies and became adults in the eighties. He’s a union guy; she’s a housewife; they have cranky World War II generation parents, they go to church out of a sense of duty and their kids lead unstructured, small town lives. They are run of the mill late 1980s Americans, that is when they were created and that is the context in which they best fit.
The show is on Season 20, but culturally speaking it’s going to enter its fourth decade next year. The characters can always be drawn the same way, but that doesn’t keep them from showing their age.