Yeah they can be if they're made to be hot for the sake of being hot. If you develop flavor with them they can be great. The tavern where I live makes ghost chili wings and they are freaking delicious. My gf's dad grows them too so we have a pretty constant supply of them.
My gf started growing some, but they got left out in the cold so we only got to harvest a couple... They were probably crossbred or something cuz they weren't as hot as they should have been
I would think that making a sauce or something with them might not be too bad, depending on what else goes into it, but the peppers on their own seem like they'd be unbearable if they were really clocking in around 1,000,000 scovilles.
I love jalapenos, cayennes, even habaneros but if you've ever rubbed your eyes after cutting even a jalepeno, it burns like hell... I'd think you'd need gloves just to handle a 1,000,000 scoville pepper