Your comment is akin to seeing someone use a paint brush to draw an orange mustache across a persons face in a photo, and then saying "does Photoshop really suck that bad??? That mustache doesn't look realistic at all".
As someone mentioned, never blame the tool, blame the user.
GB rocks for a free program, and I say this being quite familiar with Pro tools for audio recording. Pre-programmed loops will NEVER sound as good as live instruments, and in most hip-hop, rap type tunes that use them you can spot them as mile away.
GB's beauty is it gives a songwrite the ability to lay out some basic tracks, overdub some instruments, overdub some vocals, do a basic mix, export it and burn it onto a CD. It is a simple to use, powerful tool. Would you record a full pro album on it.. of course not. Is it an amazing peice of software for a free, version 1 app... you bet!