They have talked about that in commentary. Brad Bird told them early on that they should never reference real things like the 70s, music, real situations and historical things, in the show because it would date the show.
I for one LOVED the history of Marge and Homer in the 70s, and disliked the updates they made, BUT they did have to make them... sort of.
And if you watch them they aren't as bad as I thought they were at first. They aren't as great, especially the Homer being a Kurt Cobain type singer, but its not the worst thing in the world.
I am glad they referenced real things, can't imagine the show without it, but it does force them to occasionally update it.
They do "crank" out some good shows, and touching shows too. Like the one where Bart wants a brother. That was was great.
And its still better, in my opinion, than Family Guy or American Dad, and somewhat better than Futurama.
I just don't like it when they make it raunchier than it usually is, making it more like Family Guy, but that is rare. And like all shows they occasionally have a bad one I really don't like, but even those, to me, are more watchable than most other things on TV.
I hope they never go away.
Also, I really want to see a future episode where Maggie is about 25 and becomes the new Chief of Police in Springfield, with Wiggum becoming her Lou, and with Lou and Eddie still there too. They could get some popular actress with a fitting voice to be Maggie. Maybe bring back Jodi Foster. Not sure if that would be enough to carry a show, but it could be a backup story to the usual Future Lisa story.