In terms of widespread adoption of cryptocurrency, I think both are necessary because if there is no convenience, people will lose interest in adopting it. On the other hand, if I do not pay attention to security, then I will lose assets. But a general thing is that when people are new to a topic, it is necessary to explain it simply. And in the case of crypto, keeping money in a custodial wallet is initially okay and when a person gradually gains more knowledge about it, he will use a self-custodial wallet where he will have to provide his own security. Security is definitely needed, but for widespread adoption, it is also necessary to emphasize on convenience.
In cryptocurrency, the saying and reminder is "It's your key, it's your coin". Key here is private key and people only actually own their coins if they have private keys of these coins. This is only possible if they use non-custodial wallets for storing their coins, and it is impossible if they use custodial wallets with exchange accounts for storing fund.
However, this contains requirement of securing their device and wallets by themselves. Being self-custodians means they are fully responsible in security of devices, wallets and funds. No exchanges, no other parties are responsible in security of wallets and funds in case people go self-custodial.
People can ignore privacy but they must take care of security as best as possible because without enough security, their funds will be stolen someday and somehow.