Oh no! That’s not an uncommon first mistake: basically importing a finished manuscript only to export it straight back out, and wiping out tons of formatting you may have, as Scrivener is way more limited than just about any word processor. I like to think of it more as a staging tool for saving yourself as much manual labour as possible when going on to formatting. For example, its settings for handling first-line indent suppression at the beginning of a section (or even following empty line section breaks or non-para elements like block quotes) is the kind of thing that could take many hours of manual labour in Word, but it’s a few checkboxes in Scrivener.
But yes, for the next project, where you’re starting with an empty white rectangle and a blinking cursor: that’s more where Scrivener is meant to shine.
As for metadata, my advice is pretty much what you concluded. Go over the basic descriptions of what they can do for you in the user manual, in §10.4. I do try to provide a few use case examples here and there, but the focus is on each of their strengths and weaknesses, so you can figure out what will work best for what particular aspect of your work you find yourself finding difficult to see past the outline list.
Some may defy the defaults: for instance I strongly prefer using the Label field as my status indicator, because I can colour-code icons and other elements throughout the software, and thus at a glance see how a particular section is developing, as it goes from red to orange to green. I use many more colours than that, for different states, like pink for a stub that has nothing written yet and may be discarded. Warning states for bad problems that need to be fixed, etc.
Then the “Status” ends up getting renamed and used more topically, usually. It depends, sometimes I don’t use the status dropdown at all.
Sometimes these uses will even change over the course of a project’s lifespan. In the early phases, colour coding status can be super beneficial for me, but once everything goes green… maybe not so much. At that point I might transition to deleting all of those early stub-rough-revised-final draft type markers, and use them for other special conditions.
At any rate, the key is to use what makes sense to you at the time, and only if you find yourself struggling to get a good grasp on some aspect of your work. That’s my opinion anyway—I think there can be a tendency to going over the top with classification metadata, anticipating what you’ll need and spending hours on it, but in the end you never end up using any of it.
And when you think of a practical use-case, search the forum! Lots, and lots of threads have been created over the years, for how to track this or that thing, which then turn into discussions on metadata. You’ll find fewer results just hunting for topic titles on how to use metadata, because most people come in here asking “How can I keep track of the chronology of events…”, not yet knowing how to form that capability into the jargon of the software.