I go back and forth on this one. On one hand, it does not really add anything and for a long time I did not really use it. There isn't much point without an appearance system (or a more crucial one). ...
For me, clutter makes households feel more lived in. I have some "neater" houses too, just depends on the type of Sims I play.
Clutter definitely improves building for me, as I love to decorate. While it doesn't add much to actual gameplay, and I'm okay with that, it at least makes my houses look not so boring.