How to add every Adobe Font Family faster than selecting "Add Family" for each one?

I very strongly recommend NOT doing that. Sync only the fonts you need at a given time.

There are more variables than hard disc capacity that push a computer into unstable territory when too many fonts are installed. And that's just considering fonts that are installed the traditional way. Font management applications have their own pros and cons. Adobe Fonts is more of a cloud-based thing. Internet connection bandwidth becomes an additional factor.

Then consider the extra steps Adobe application users now have to take to make synced Adobe Fonts available to all applications in a computer. You add them at the Adobe Fonts website. But then you have to open the Adobe CC desktop app to "install" them for all applications. Scrolling through that fonts list is big pain in the neck only with a couple hundred fonts synced. It would be sheer torture trying to install many thousands of Adobe Fonts for all apps to use. After so and such many days you would have to go through that fonts list and re-install any fonts you weren't using since the Fonts service deactivates any fonts that haven't been used after a certain period of time.

Let's also not forget that new type families are added on a fairly frequent basis. Sometimes other type families (or whole libraries) are removed. Adobe has to negotiate with dozens of type companies to populate the list of fonts we can use. It would be a sheer losing game of futility to try to keep the entire library of Adobe Fonts synced on a computer.

Trust me, it's best to just add type families when they're needed and remove them when they're not being used. It's very very easy to reactivate a type family that has been previously removed. There is no need to install the entire library.