Hey, are you saying that you don't trust you coins on Coinbase? All the reputable firms do their transactions there. I assumed that it might be safe there rather the an online wallet.
He is saying Coinbase is reputable. However, keeping your coins/tokens off Coinbase or exchanges in general and in a wallet will allow you access to your funds at all times. If you want to buy sell or trade in general you can find somewhere else to do it in the times Coinbase or anywhere else runs into an issue.
Think of what happens when you attempt to take over 1500 or more from an atm. Banks will restrict how much money you take out daily. In crypto, you always have access to your funds as long as it is in your wallet and you have the keys to the wallet.
If you are not responsible enough to put your key somewhere safely, I'd honestly recommend keeping your funds on a reputable exchange. It is the same trade off as using a bank though and if something happens to the exchange clearly you'll lose your funds, but losing your password to your account shouldn't be an issue. Get in contact with customer service and you'll get a new password and access to your funds
If you are responsible enough to secure your key, not putting your funds on an exchange provides more freedom but there is no customer service to get your forgotten keys and your funds will be lost.
As a person who lost his key with 30000 plus worth of Dash, I'll tell you it's the worst feeling ever. For two weeks before and after work I'd spend every minute trying to figure out my key. Luckily I was fortunate enough to finally figure out my key after hours of writing down different combinations of words. People have lost millions in crypto the same way. Most of my funds are in a wallet but there are still risk associated with doing so.
Alot of hard-core crypto users are against exchanges or banks due to major events in the space where large exchanges failed. However, you really do need to know who you are as a person. If you tend to forget alot or lose shit regularly or just have kids/pets around, you may consider just leaving it on an exchange or do a combination of both a wallet and exchange. People will talk that crypto shit , but as soon as you lose your keys most will throw it in your face and be happy more of the supply is out of circulation.
End of the day do what is right for you.