If you had bitcoin held on FTX, there is no amount of money or time that will bring those coins back. They are gone. You have a 0% chance of finding those bitcoin.
Even in the worst case scenario, self-custody is better than an exchange.
To me it sounds like the opposite. The exchange and its owner legally owe money to users, and there's some chance that the users will get at least some portion of their money if the government will manage to seize anything. But with self-custody if you lost your keys, it's not likely you'll see them again.
But typically in both cases the worst case is losing your coins forever, and it seems to also be the most common outcome when something go wrong.
Self-custody is better than custodians because when it's done right, the chances of losing your coins are significantly lower. And it's not rocket science, people need to just use their brains and create multiple backups, instead of writing down the seed, putting it in a cabinet, then accidentally throwing it away with garbage during cleaning.