Yes, this is specifically a problem with formkit when enable_simplified_category_creation is enabled, plugins will need to migrate to use formkit and the new data structure.
there’s a working example of this in one of our core plugins, which was migrated here:
you can see how the form structure branches with {{#if this.siteSettings.enable_simplified_category_creation}} and how the form if structured using formkit and data from @outletArgs.form. The old form structure is still there after {{else}} for legacy support.