Don't know if this has been requested, but the ability to organize info into columns. One of the issues I had with classic wordpress was that organizing information on posts and pages into columns was impossible without a plugin, raw code or a theme. I need the ability to organize my info into columns because my sites contain too much info that needs to be organized. I'm not a php developer, and having to manually type in div classes is a time wasting pain in the #%/.
Are you talking about the front-end or the admin pages? If you are talking about the front-end, that is very much the theme's job and should not be part of core. It sounds like you'd need a theme that uses CSS Grid.