The PHP templates for all post types thing reminds me of term meta from the last major update; a rather obvious feature whose non inclusion in past versions didn't really make much sense. Surprised it took from WordPress 6.5 years to add the ability to choose templates for custom post types.
Custom CSS in the customiser is pretty neat.
And yeah, the REST API endpoint updates are nice to see as well.
Why would any major WP site integrate a REST API if it means their content is going to be accessed without the gateway of advertisements on their own site? Ya it'd be flipping fantastic if people made aggregators for good sites with the new features, but isn't it a direct conflict with business interests?
a REST API doesn't necessarily mean outside access. For one thing, it’s a quick conduit for React and Angular front ends. I've had countless requests for this kind of thing — in fact, this API makes a hacky plugin of my own thankfully obsolete.
Beyond existing sites, the REST API means that Wordpress can be used as a quick-and-dirty back end to datasources that are not necessarily bloggy. Folks use Wordpress for things beyond blogs because they don't want to build custom CMS's, now this CMS has a whole new field of possibilities it can fulfill.
The plugin's no longer required, and is a no-op if you activate it on 4.7. We're still working out the plan going forward, but likely it will become where we test out beta code and new endpoints.