Depends what you are protecting yourself from.

If you are worried about someone suspecting that you have bitcoin, this is definitely not the way.

Coinbase knows your identity and how much you have bought. Whether you sold it all or not, your government identity is associated with buying bitcoin and therefore you may be a target just for that:

1. Coinbase leaks your account info, even if you never bought any Bitcoin from them, your personal info is associated with bitcoin (crypto really) so a thief or other criminal or motivated acgjvist in the future might attack you.

2. Coinbase is likely to report your activity to various government entities, they may target you, either by choosing to surveil you, or looking at your lifestyle and deciding for themselves if they think you are tax evading etc.

So even if you coinjoin, no one knows where your money is, they don't know whether or not you have spent it and you have deniability, but you also have association and if they place it on you to prove your spends, because they know of your buys, they can't take the Bitcoin if they can't find it, but they can make your life a living hell by attacking, arresting or inflicting other pain upon you in the hopes you give up your wealth for "freedom".