You have to provide strong evidence about CoinBase is a scam, while some people here say CoinBase is a good exchange on the Crypto market. as far as I know coinbase is the most liked place for many people to do trading there.
They have
https://pro.coinbase.com/ which most of the trading happens.
Coinbase is probably the most secure and robust platform in the world of cryptocurrency. I've been using it for more than a year and I've never had any trouble.
AFAIK, yes they are one of the most secure and well known company and good to know that you haven't experienced any bad thing to them. But I reckon what leea is telling you, you shouldn't rely to an exchange as your wallet. You may not know what will happen inside them in the future, you better hold your private keys/seeds.