I'll give you an example: party chat. Works just great on the 360, right? Send a friend and invite, they accept, you talk. It's been working for ten years, why change it? Well, change it they did. I forget the details, because it was at launch and they've since fixed it, but party chat just didn't work the way it used to, and I'd argue it worked in a broken manner.
But, yeah, the Xbone is worse. Primarily, IMO, worse because you are no longer the customer, AFAICT. I wouldn't be surprised if suddenly a "whack the monkey for a FREE month of XBL!" banner showed up on the dashboard. But there are some serious usability issues in there, too.