I know the bank as much flaw especially commercial bank like First bank, GT, etc. Thank God for fintech like Opay, Palmpay and Kuda. That aside, CEX has their own flaws.

They charges you fee that can be questionable sometimes depending on the service you want example:
Look how Bitget took advantage of the limited p2p exchanges available in Nigeria from top CEX and then charges 0.5% or 0.05% for every p2p transaction.

Also, another thing is that your coins in these CEX (Centralise exchanges) are not yours, since you don't own the seed phrase/key, NOT YOUR KEY = NOT YOUR COIN. While you can have your coins here, just has how bank may question where you received your funds and ceased till everything can be clarified, CEX is no difference, know this and avoid another danger.

The best is Non-Custodian wallet, where you have your key and full control of your coins and this is a better way of keeping funds rather depositing all  in the bank. It even gives an hedge against inflation and also a better ROI than what a bank may promise to give, and this is more likely when you invest in bitcoin, but all your funds there in case of emergency and then there is a dip or being in the bear market then you may end up selling in lost. Although, one thing is sure HODLing bitcoin for a long term( at least five years) is far better than any ROI from bank and many others.