We do fall short on a protocol level.
We don't fall short on a protocol level, there's multiple coinjoin protocols that provide privacy on Bitcoin.
That does not mean that giving up custody is a necessity. It's simply a choice, given certain tradeoffs.
When you used the word
"require", you implied
"necessity" which is the opposite of
"choice".Nonetheless, there exist legit services which require you to forfeit custody, and you'll have to grasp that part.