Exchanges are exactly like banks. You don't own your private key and just depend on third trusted party, coinbase is a good exchange since they give good service for buying and selling. But it is not a good idea to store in exchanges since you don't have the full control over your fund. Even an exchange has a good reputation to trust with we are missing the point why Bitcoin is made which is to free us from thrid trusted party. It still best to choose a hardware wallet or an open source wallet like HODLER which also has retail feature to offer. Still, coinbase is good as exchange but not as a bank.
I also agree with this. Coinbase require you to subvert your privacy by enforcing KYC/AML. It goes against the principles of cryptocurrency, where the whole point is to provide sovereign, decentralized, censorship resistant money. With Coinbase, even if it is not compromised, your funds and account can be locked for any reason, and we've seen instances of it in the past. To ensure maximum security I would stick to using decentralized exchanges like Bisq or Localbitcoins and keeping your funds only in Open Source wallets like Bitcoin Qt for Bitcoin or HODLER for multiple coins and tokens.