Seems a very odd choice for Twenty Twenty Two not to include easier access to the good old Customizer – since 1), at least as far as I could discover, there’s no simple way to override certain theme defaults, and 2) it seems a major step backward in terms of usability to have to go back to editing a text file, whether style.css or theme.json.
In my case, I simply wanted to get rid of the default padding that affects the entire site via .wp-site-blocks, and trying to zero it out via Global Styles had no effect.
I’m guessing there are already plugins available, or soon-to-be-available, for getting the customizer back for block themes – like the Classic Editor plugins were, and by many people still are, preferred when Gutenberg was rolled out. Maybe in the short term can just add/restore the customize.php link to the admin bar.