Sitecore SXA : Your site has been exported in Wireframe mode. This mode does not reflect your site’s look and feel and may cause problems for importing and editing.
When i try to export, Site themes getting above error
This happens if you export when your View mode is set to wireframe. You need to select Experience Accelerator ribbon > View Mode > Selected Theme. You may need to set a theme first using Experience Accelerator ribbon > Theme.
See The View Modes for SXA 1.9 for the full background.