I’m talking about DeFi - distributed exchanges, yield generating savings accounts, and collateralized loans. Additionally ERC20 stables so on and off ramps are significantly less important. I see Coinbase’s primary function as an exchange and a way to convert to dollars. Both are threatened now. They have low fees, low latency, and more usability... but will that last?

Could be true, but the "de" in "defi" prevents it from killing Coinbase's main purpose, which is being the fiat -> crypto gateway.

True, it is a challenge do do a decentralized on/off ramp. But it is also questionable if that’s worth $100B valuation, too, without everything else they do.

It probably isn't itself, but as long as they're able to provide an attractive centralized alternative to the things happening in defi, they can capture a lot of that growth. Custody, trading, wallet, etc.

A successful model for Coinbase at this point is probably what Google does: let others innovate, clone the ideas once they start becoming popular, keep them under an umbrella and provide easy integration/movement among them.