Trying to get “just my user fields” sounds simple, but we may need to know more. If you get all fields from all non-system tiddlers, and then you later import a tiddler for some random utility purpose, or a plugin, etc…, you may suddenly complicate your list of fields.
I would suggest having a filter that gets all fields from tiddlers under a certain tag (or all tiddlers meeting some other filter condition that captures typical tiddlers for the workflow you have in mind here)…, and then subtracting out the ones that are unwanted.
Then you’d have an expression like [tag[people]fields[]] -title -creator -modifier -modified -created -text -type -tags
Another approach is to have, in some utility tiddler, a list of the actual fields that are relevant to the purposes you have here. If you use tags in your workflow, the tiddler for that tag is a nice place to store something like a list of fields that will be needed for some tag-relevant workflow. Make an actual tiddler at that tag node, and make a custom field there to manually list key-fields.
[{people]get[key-fields]]
Of course, then this list would not be automatically updated if you further expand your solution to add a field for each person’s website, or their position title, or whatever. But there would be one clear place to update that list — or to trim it, if you realize some field is no longer relevant.