I own two Xenforo licenses - and I still think, that Xenforo is the best forum software available. But is becomes more and more outdated on the front-end. Responsive design only is no longer enough. We need features like a touch-optimized mobile version, a mobile optimized composer (floating) and infinite scrolling. I know that some of these features could be implemented by an optimized theme. But I was not able to find such a theme - and I think that the standard theme should also be up-to-date and innovative.