Well in principle you should't keep your coins in cex, and if you are tech-savvy enough, obviously self custody is the best solution. And everytone should try to learn it if they haven't yet.
But i wouldn't recommend self custody to my mom for example who barely understands how to work with a different browser. I am pretty sure that he would lose the private key and the backup if she used cold wallet. And if she used desktop wallet i couldn't guarantee she wouldn't get hacked at some point.
well, you have a good point on this matter. it depends on the person who is holding the funds. not many people are trusting their capability of holding their keys, this is why some people still store their funds in CEXs. but for those regular crypto users/traders, we need to remind ourselves not to store funds in CEXs for long time. better secure it in our own wallets.