There are Tolkien rip offs, but Tolkien didn’t invent fantasy, and unlike a lot of fantasy authors Sanderson doesn’t include elements like dwarfs, or elves or really anything that Tolkien came up with as far as I can tell. Are you maybe confusing him with someone else?

If you're including Game of Thrones and Wheel of Time, then I guess Sanderson broadly falls into that same category. I'd hardly label any of them "rip-offs", though, especially given that there are books out there blatantly ripping off Tolkien right down to elves, dwarves and halflings.

I’ve only read the Mistborn series, but I didn’t find it all similar to Tolkien–not in style or themes.

By "Tolkien ripoff", do you mean anything beyond "fantasy novel"?