Not really true for Raspberry Pi 2. I'm running it with Kodi@OpenELEC next to my TV, it's set-up to connect to NFS via WiFi served by one of the SOHO Mikrotik routers. On the other end Synology DS215j NAS is cabled in via 1Gbit. No hiccup on 1080p/720p whatsoever despite WiFi choker, but haven't tried anything bitrate-crazy yet.

(For physical media I still just use a PS3.)