The problem is that custodial apps and KYC is that they can ban you or block your txs, or just charge fees, or simply not be an option in certain countries. What you are saying is like saying that everyone can just use Coinbase and ask for their debit card, none of these are solutions to someone who really needs bitcoin. Can someone in Iran use these apps? Lol. As for just using onchain for holding and nothing else how much can you buy and self custody if the fees become 500usd or 1k?