Not really. Plenty of people don't know how to properly mic a cab, or don't mic it to the taste of another person. I've also heard plenty of guys who made profiles of their amps & cabs with their guitars and the sound samples sounded awful to my ears. But this is subjective. Still, it's not that all profiles sound great and the only problem is that you're not using the right guitar or pickups.
You have a point that it most matters how a guitar sounds in the mix, but the sound itself should inspire you to play. You can always tweak a tone to fit in a mix, it just may take more work. And it depends what kind of mix you're talking about.
I don't deny there are some bad and even really, really bad profiles. I've downloaded countless of them from the free rig download in the past. I was thinking about commercial profiles you find here on this forum. Okey I should probably said that but it was nearly 03.00 am here and I was drunk too. Well at least my spelling wasn't that bad as can happen when drunk, even in ny native language.