If you think pop/ rock & roll are the center of the universe, they are a huge deal. The certainly raised the bar on creativity within rock and roll.

If you understand that rock and roll at its heart revolves around some pretty basic conventions and limitations, you're left with one inconsistent singer songwriter, and an exceptional jingle writer. These two are connected with some imaginative producers/arrangers at a pivotal moment in the history of pop music.

For better or worse, they (and Dylan) established the idea of the popular singer-songwriter... which ultimately lowered the bar on both professions. If you look at the history of popular song before them- especially what is called "The great American songbook" you find much more harmonic variability, executed by higher caliber musicians.

Also, by the time they folded rock was outgrowing them with acts like Yes, King Crimson, and Frank Zappa, all of whom saw possibilities for rock beyond the pop song format.

Do I think they're overrated? IDK. I don't really care. They are. I listen to their music once or twice a year, and enjoy it a lot during that time. There's otherwise just so much else out there.