It is almost impossible to escape a properly sunk kesa from a skilled opponent. The problem with traditional kesa is definitely not that it can easily be escaped. The problem is that it doesn't have great transitions. In sports where you can win by pinning, this is not a problem, but for BJJ, it is not usually ideal. Notice that Barnett used the kesa at the very end of the match, btw ... this was smart use of the clock by him, he didn't need any transition options at that point.
Btw, there are tons of different kesa escapes people will show you. The problem is that, like so many grappling moves, they don't actually work in high-level competition. In actual high-level judo competition, the only kesa escape that works at a high percentage is turning into the guy and going to your knees. I have read an analysis of high-level judo competitions where they analyzed pin escapes. When osaekomi (pin) is established, the bottom guy escaped only 1/3 of the time. When he did escape, in 100% of the cases it was by turning in and escaping the arm. Not one bridge roll, not one "kesa to kesa," not one armbar counter. Those are gym escapes; I use them all the time myself, but against a high level competitor, you must defend earlier by defeating the control and turning in, not letting a strong pin get established. If you let it get established, you are fucked.