I had a couple friends in high school who were into jazz. Around this time, Harry Connick Jr. started selling a lot of records crooning in front of his big band. I wasn't impressed. I didn't have any interest in jazz and from what I could tell, this was a pin-up boy singing love songs with a big band in back of him.
One day, my classmate was talking about one of the jazz artists he was into and a girl in front of him asked what he thought about Harry Connick Jr. Because this guy wasn't me, he politely sidestepped the question. She kept asking him and made some kind of bold statement about Connick being an all-time great. My friend was unflappable. He remained kind but told her he was pretty sure Harry Connick Jr. would starve if he was working during the same time as all the people he was ripping off. I don't know if that's true or not, but I nearly fell out of my chair laughing. It's still one of my favorite stories to tell and one of my favorite lines to use.
There are an impossible number of garage bands and bar bands who have ripped off the blues without ever having understood what the idiom is all about. In other words, there are a lot of bands who'd starve if they were working back when the legends built the beast that is the blues. They'd never stand a chance.
One band who could and actually did was the Rolling Stones. The Stones aren't a blues band but in their early days they listened to Muddy Waters and Elmore James. They weren't copying bands copying bands who copied Waters and James. They went right to the source and connected to it.
Listen to "Fancy Man Blues," a number they recorded years ago that set unreleased until it surfaced on a rarities package a few years ago. Listen to Jagger's killer harmonica solo. You could play that for a lot of blues purists and they'd guess a lot of great names before you finally let them in on the secret and told him was actually playing. That's not a copy, that's blues with a feeling.