I think you touched upon the reason without realizing it: it's popular in a lot of the deep fried / layers of irony memes that I see because its understood as a mediocre show for boomers.
Like, the animation has aged poorly and the humor is outdated, but the characters are recognizable. I think the humor of these kinds of memes comes from seeing the show's characters in a different context of humor than what they are normally in. Like, I can picture a meme of Brian holding a margarita glass with the bottom text being something like "doodoo ass." If you made a meme of Peter Griffin, running away from a picture of Chiang Kai-shek and saying something like "No Mao don't stop until you capture Taiwan," people here would probably think it's funny, not because it's related in any way to the show, but because it's disconnected from that show. Idk, I think that is at least an aspect of it